Background <p>Sedentary behavior (SB) is a critical health indicator independent and interactive with physical inactivity. While the application of psychological theories to understand and intervene in physical activity is robust, summary evidence for psychological theories applied to SB is minimal. Therefore, this systematic review aimed to describe and appraise the effectiveness of psychological theories applied to predict and change SB.</p> Method <p>Eight databases were searched for studies using psychological theories to modify or predict SB among adult participants. Studies were separated by observational (<i>k</i> = 20) or experimental (<i>k</i> = 19) design and categorized into five theoretical frameworks: social cognitive (<i>k</i> = 15), action control (<i>k</i> = 11), dual process (<i>k</i> = 9), stage models (<i>k</i> = 3), and humanistic (<i>k</i> = 1). Study characteristics, design, theoretical framework, SB measures, and effect sizes were extracted and analyzed. The qualities of the papers were evaluated using the risk of bias tools.</p> Results <p>The search retrieved 39 eligible studies. For observational studies, only two frameworks had sufficient evidence of their effectiveness in predicting SB: the social cognitive (median explained variance = 18%) and dual-process (median explained variance = 14%) frameworks. For experimental studies, the social cognitive (median <i>d</i> = −0.29), action control (median <i>d</i> = −0.43), and dual-process (median <i>d</i> = −0.56) frameworks showed promise in reducing SB, while the stage models and humanistic frameworks did not have sufficient current evidence. While all observational studies had above fair quality (<i>k</i> = 20), 10 out of 19 experimental studies (nine randomized and one non-randomized trials) were at high risk of bias.</p> Conclusion <p>The current results show promise of several psychological frameworks’ ability to predict and change SB. However, there are opportunities to increase the quality and diversity of theory. Thus, future studies should employ various theoretical frameworks, such as the humanistic and stage models; standardize the reporting of effect sizes; and apply more methodological rigor to better examine the relationships between psychological theories and SB. Additionally, future studies need to investigate different types of SB as they may have different underlying theoretical antecedents.</p>