Objectives: In the current study, we (a) describe naturally occurring changes in self-presentation processes (i.e., impression motivation, impression construction) and moderate-to-vigorous intensity physical activity (MVPA) over a period of 6 months among women who were treated for breast cancer; (b) evaluate the associations of cancer-specific factors with self-presentation processes and MVPA; and (c) examine the within-and between-person associations of self-presentation processes with MVPA. Method: For this prospective longitudinal study, women (n = 128; M-age = 55.14 years) completed questionnaires posttreatment for breast cancer (M-time (since) (treatment) = 3.96 months), as well as 3 and 6 months later. Results: Based on the findings of the multilevel analysis, self-presentation processes remained stable over time, whereas MVPA levels changed over time (B-linear = 6.11, SE = 2.44, B-quadratic = -3.41, SE = 1.23). Radiotherapy was related to impression motivation (B = -.40, SE = .19) and impression construction (B = -.45, SE = .15), and chemotherapy was related to impression motivation (B = .31, SE = .15). Impression motivation was associated with MVPA at the between-person level (gamma(01) = 5.72, SE = 1.22), and impression construction was associated with MVPA at the between-and within-person levels (gamma(01) = 3.45, SE = 1.49; gamma(10) = 3.67, SE = 1.66). Conclusions: This study provides insight into the patterns of self-presentation processes and MVPA during early cancer survivorship, as well as the associations between these constructs at the within-and between-person levels. Based on these findings, more research is needed to determine whether self-presentation processes should be conceptualized as state or trait characteristics or as having both components, and extend the self-presentation framework to incorporate additional explanatory variables as this might provide a more complete explanation of MVPA.