This Campbell systematic review examines the effectiveness of women's economic self‐help groups (ESHG) on individual women empowerment in low‐and middle‐income countries. It also examines the mechanisms that empower women through female participants' experiences of ESHG membership. The review summarises findings from 23 quantitative studies and 11 qualitative studies. The vast majority of these studies was conducted in South Asia. ESHG have positive effects on women's economic and political empowerment, as well as social empowerment ‐ such as, women's family size decision‐making power and social mobility. There is no quantitative evidence to indicate positive effects on women's psychological empowerment. However, the qualitative studies suggest that women participating in ESHG perceive themselves as psychologically empowered. ESHG with a training component, such as financial and business education or life skills training, have a larger effect than programs that do not involve training. Important mechanisms which facilitate empowerment are gaining financial skills (economic empowerment); gaining the capability to speak in front of others, access to household decision‐making (psychological empowerment); improved networks and the experience of mutual support from and solidarity with fellow group members (social empowerment); and access to wider social participation combined with an increased understanding of political contexts and individual rights (political empowerment). There is no evidence of increased levels of domestic violence. Qualitative data indicate that ESHG may decrease domestic violence as women gain respect from their partners, families and access to household decision‐making. Few qualitative studies report experiences of disappointment, mistrust and stigma among women who attended ESHG. ESHGs do not reach the poorest citizens. The ‘poorest of the poor’ do not participate for economic and religious reasons, and mechanisms of self‐selection. Plain language summary Motivation: Self‐help groups (SHGs) are implemented around the world to empower women, supported by many developing country governments and agencies. A relatively large number of studies purport to demonstrate the effectiveness of SHGs. This is the first systematic review of that evidence. Approach: We conducted a systematic review of the effectiveness of women's economic SHG programs, incorporating evidence from quantitative and qualitative studies. We systematically searched for published and unpublished literature, and applied inclusion criteria based on the study protocol. We critically appraised all included studies and used a combination of statistical meta‐analysis and meta‐ethnography to synthesize the findings based on a theory of change. Findings from quantitative synthesis: Our review suggests that economic SHGs have positive effects on various dimensions of women's empowerment, including economic, social, and political empowerment. However, we did not find evidence for positive effects of SHGs on psychological empowerment. Our findings further suggest there are important variations in the impacts of SHGs on empowerment that are associated with program design and contextual characteristics. Findings from qualitative synthesis: Women's perspectives on factors determining their participation in, and benefits from, SHGs suggest various pathways through which SHGs could achieve the identified positive impacts. Evidence suggested that the positive effects of SHGs on economic, social, and political empowerment run through the channels of familiarity with handling money and independence in financial decision making, solidarity, improved social networks, and respect from the household and other community members. In contrast to the quantitative evidence, the qualitative synthesis suggests that women participating in SHGs perceive themselves to be psychologically empowered. Women also perceive low participation of the poorest of the poor in SHGs due to various barriers, which could potentially limit the benefits the poorest could gain from SHG membership. Findings from integrated synthesis: Our integration of the quantitative and qualitative evidence suggests there is no evidence for adverse effects of women's SHGs on the likelihood of domestic violence. Women's perspectives in the qualitative research indicate that even if domestic violence occurs in the short term, in the long term the benefits from SHG membership may mitigate the initial adverse consequences of SHGs on domestic violence. Executive Summary BACKGROUND Women bear an unequal share of the burden of poverty globally due to societal and structural barriers. One way that governments, development agencies, and grassroots women's groups have tried to address these inequalities is through women's SHGs. This review focuses on the impacts of SHGs with a broad range of collective finance, enterprise, and livelihood components on women's political, economic, social, and psychological empowerment. OBJECTIVES The primary objective of this review was to examine the impact of women's economic SHGs on women's individual‐level empowerment in low‐ and middle‐income countries using evidence from rigorous quantitative evaluations. The secondary objective was to examine the perspectives of female participants on their experiences of empowerment as a result of participation in economic SHGs in low‐and middle‐income countries using evidence from high‐quality qualitative evaluations. We conducted an integrated mixed‐methods systematic review that examined data generated through both quantitative and qualitative research methods. SEARCH METHODS We searched electronic databases, grey literature, relevant journals and organization websites and performed keyword hand searches and requested recommendation from key personnel. The search was conducted from March 2013–February 2014. SELECTION CRITERIA We included studies conducted from 1980–January 2014 that examined the impact of SHGs on the empowerment of and perspectives of women of all ages in low‐ and middle‐income countries, as defined by the World Bank, who participated in SHGs in which female participants physically came together and received a collective finance and enterprise and/or livelihoods group intervention. To be included in the review, quantitative studies had to measure economic empowerment, political empowerment, psychological empowerment or social empowerment. We also examined adverse outcomes including intimate partner violence, stigma, disappointment, and reduced subjective well‐being. We included quantitative studies with experimental designs using random assignment to the intervention and quasi‐experimental designs with non‐random assignment (such as regression discontinuity designs, “natural experiments,” and studies in which participants self‐select into the program). In addition, we included qualitative studies that explored empowerment from the perspectives of women participants in SHGs using in‐depth interviews, ethnography/participant observation, and focus groups. DATA COLLECTION AND ANALYSIS We systematically coded information from the included studies and critically appraised them. We conducted statistical meta‐analysis from the data extracted from quantitative experimental and quasi‐experimental studies, and used meta‐ethnographic methods to synthesize the textual data extracted from the women's quotes in the qualitative studies. We then integrated the findings from the qualitative synthesis with those from the quantitative studies to develop a framework for assessing how economic SHGs might impact women's empowerment. RESULTS We included a total of 23 quantitative and 11 qualitative studies in the final analysis. Initially, we reviewed 3,536 abstracts from electronic database searches and 351 abstracts from the gray literature searches. We found that women's economic SHGs have positive statistically significant effects on various dimensions of women's empowerment, including economic, social and political empowerment ranging from 0.06‐0.41 SD. We did not find evidence for statistically significant effects of SHGs on psychological empowerment. We also did not find statistical evidence of adverse effects of women's SHGs. Our integration of the quantitative and qualitative evidence indicates that SHGs do not have adverse consequences for domestic violence. Our synthesis of women's perspectives on factors determining their participation in, and benefits from SHGs suggests various pathways through which SHGs could achieve the identified positive impacts on empowerment. Women's experiences suggested that the positive effects of SHGs on economic, social, and political empowerment run through several channels including: familiarity with handling money and independence in financial decision making; solidarity; improved social networks; and respect from the household and other community members. Our synthesis of the qualitative evidence (key informant interviews and focus groups) also indicates that women perceive there to be low participation of the poorest of the poor in SHGs, as compared to less poor women. IMPLICATIONS FOR POLICY, PRACTICE AND RESEARCH For Policy: SHGs can have positive effects on women's economic, social, and political empowerment. However, we did not find evidence for positive effects on psychological empowerment. These findings indicate that donors can consider funding women's SHGs in order to stimulate women's economic, social, and political empowerment, but the effects of SHGs on psychological empowerment are less clear. Women SHG members perceive that the poorest of the poor participate less than other women. In part, this might be because the poorest of the poor are too financially and/or socially constrained to join SHGs or to benefit from the financial services most often provided through SHGs. Other barriers such as class or caste discrimination might also be present. Poorer or marginalized women may not feel accepted by groups that are made up of wealthier or more well‐connected community members. It is important for policy makers to identify ways to build in support and reduce barriers for individual women who want to participate in SHGs but who do not have the financial resources or freedoms to join. For Practice: We do not find evidence for adverse effects of women SHGs on domestic violence based on the integration of the quantitative and the qualitative evidence. Although there may be adverse consequences in the short term, analysis of women's reports suggest that SHGs do not contribute to increases in domestic violence in the long term. Furthermore, participation of the poorest of the poor in SHGs may be stimulated by incentives. These incentives could be financial, for example, by giving the poorest of the poor the opportunity to participate without a savings requirements, or non‐financial, for example, by stimulating the husbands or mothers‐in‐law of the poorest of the poor to let their spouses and daughters‐in‐law participate in SHGs or conducting outreach activities to marginalized groups. As new programs are implemented in different contexts, it is also important that program designs are tailored to the local settings in ways that allow them to evolve over time. This review has shown that one‐size does not fit all, and while it is important to take best practices across programs for implementation, this means that flexibility is required to adapt programs successfully for the greatest impact in women's lives. For Research: There is a need for more rigorous quantitative studies that can correct for selection bias, spillovers and the difficulties of measuring empowerment. There is also a need for more research, focused on examining possible factors that meditate and/or moderate the impact of SHGs on women's empowerment to further understand the pathways or mechanisms through which SHGs impact empowerment. For the latter it is crucial to conduct rigorous qualitative research in addition to rigorous quantitative research. Whereas quantitative research is useful in understanding certain aspects of the impact of SHGs on empowerment, qualitative studies could show us more nuanced ideas about how to measure empowerment. Importantly, both quantitative and qualitative studies need to describe more fully the various components of the SHGs being studied. Greater detail in the description of the program design will help in determining moderating factors in the design of SHGs.