Meta-analysis is a prominent method for estimating the effects of public health interventions, yet these interventions are often complex in ways that pose challenges to using conventional meta-analytic methods. This article discusses meta-analytic techniques that can be used in research syntheses on the effects of complex public health interventions. We first introduce the use of complexity frameworks to conceptualize public health interventions. We then present a menu of meta-analytic procedures for addressing various sources of complexity when answering questions about the effects of public health interventions in research syntheses. We conclude with a review of important practices and key resources for conducting meta-analyses on complex interventions, as well as future directions for research synthesis more generally. Overall, we argue that it is possible to conduct meaningful quantitative syntheses of research on the effects of public health interventions, though these meta-analyses may require the use of advanced techniques to properly consider and attend to issues of complexity. Expected final online publication date for the Annual Review of Public Health Volume 39 is April 1, 2018. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.