This is the first of three briefs that aim to inform the field of two-generation approaches. This brief describes how two-generation initiatives participating in NS2G developed and refined a two-generation logic model to help them identify the right mix of services for primary caregivers and their children. This brief is intended for readers who want to develop a two-generation logic model. Logic models are diagrams that help initiative leaders and staff (1) articulate their plans for services, including the intensity, duration, and quality of services, (2) ensure that the plans line up with the expected outcomes for parents and children, and (3) identify expected outcomes and the associated measures for the outcomes (Ross et al. 2018). This brief includes a blank copy of a two-generational logic model template (Appendix A) in addition to instructions and guiding questions for initiative leaders and staff to consider during logic model development (Appendix B). (author abstract)