Time has been considered as a key success criterion and a constraint demanding prioritization between projects. It also creates competition among the projects in a portfolio and tensions across time horizons in portfolio decision-making. Thus far, research on project portfolios and their management has treated time only implicitly and secondarily. The purpose of this conceptual study is to investigate the relevance, meaning, and future possibilities of time in project portfolio management research. The relevance and treatment of time is first covered generally in project and management studies, to guide the conceptual analysis of project portfolio management research. Then, the objective, subjective, and contextual considerations of time in project portfolio management are mapped to summarize extant threads of research. The findings offer novel ways to conceptualize project portfolio management and reveal the connectedness of objective, subjective, and contextual views of time as a central driver of dynamics in project portfolio management. This study suggests supplementing and combining the mechanism, practice, and actor-centric project portfolio management studies with those concerned with time. Future research avenues are proposed both combining the objective, subjective, and contextual views as well as treating each view separately.