The chapter provides an up-to-date and relatively comprehensive treatment of procedures for assessing mediation and moderation in social-personality psychology. It discusses a more in-depth treatment of mediation, including underlying assumptions, estimation, statistical inference, and power considerations. The chapter discusses basic models assuming homogenous errors and more complex multilevel models that allow grouping and nonindependence of observations. It focuses on testing and interpreting moderator effects. The chapter defines the moderation and also discusses its relationship with statistical interactions. It describes the basic models used to test for interactions and moderator effects. The chapter examines how one interprets the results of these models and best practices for the presentation of moderator effects, and also describes the issues that complicate the search for moderator and interaction effects, focusing in particular on considerations of statistical power. The chapter explains the integration of two processes, framed as either moderated mediation or mediated moderation.