A common theme that has emerged from classic and contemporary theoretical work in both the fields of personality and relationship science is a focus on process. Current process-focused theories bearing on personality invoke a view of the individual in ongoing action and interaction with the environment, reflecting a flow of experience rather than a static depiction. To understand the processes by which personality interacts with the social environment (particularly dyads), investigations must capture individuals interacting in multiple interpersonal situations, which likely necessitates complex study designs and corresponding data analytic strategies. Using an illustrative simulated data set, we focus on diary methods and corresponding individual and dyadic multilevel models to capture person-situation interaction within the context of processes in daily close relationship life. Finally, we consider future directions that conceptualize personality and close relationship processes from a dynamical systems theoretical and methodological perspective.