Although the independent within-person association between physical activity and sedentary behaviour with valence in daily life has been extensively studied, few studies have used compositional data analysis to examine how different movement behaviour compositions are related to valence in daily life. This study aimed to examine the within-person association between wake-time movement behaviour compositions with affective valence and the extent to which replacing time spent sedentary with physical activity was associated with valence within individuals in daily life. A 7-day ecological momentary study design was used whereby 94 Canadian university students (Mage =19.45, SD = 2.21, 78.7% female) reported on affective valence using an adapted version of the Feeling Scale at 7 randomly timed prompts each day. In addition, activPAL accelerometers were worn continuously by participants on their right thigh for the duration of the study to determine time spent engaging in sedentary behaviours and physical activity. Compositional data analysis with isotemporal substitution models were used to examine the within-person association between movement behaviour compositions and affective valence. The within-person association between movement behaviours and affective valence was weak (r2 = .013). Nevertheless, engaging in less sedentary time than usual and instead engaging in physical activity was significantly related to more positive affective valence. Considering light intensity physical activity (LPA) and moderate-to-vigorous intensity physical activity (MVPA) separately, replacing time spent sedentary with time engaged in MVPA and LPA both had a significant positive association on affective valence, although the association with MVPA was stronger than the association with LPA. The results provide unique insights into how replacing sedentary time with physical activity in daily life, especially MVPA, may be associated with more feelings of pleasure. These results may be useful to help inform the development of just-in-time adaptive interventions.