Most development interventions are complex, comprising several interacting activities affecting multiple outcomes. Impact evaluations of such interventions are widespread, but the literature offers little guidance on how to assess the cost-effectiveness of such integrated projects. We review the literature that conducts cost-effectiveness analyses of multiple interventions alongside impact evaluations in low- and middle-income countries. Only seven studies are identified in areas as diverse as de-worming, school support, conditional cash transfers, early childhood development, and social funds. We find that none of the applied approaches can be effectively employed in all instances, though each of them can be applied in some special cases. Furthermore, none of the studies reviewed addresses output synergies. Given the rising numbers of impact assessments in development practice and their importance for policy, research needs to develop sound methods to assess the cost-effectiveness of integrated interventions.