Rationale <p>Contemporary theories of addiction postulate that persistent cannabis use develops in part through the positive and negative reinforcing effects on affect regulation. However, while much research has focused on affect as a stimulus for use, a dearth of research has explored acute cannabis effects on changes in affect in the natural environment. </p> Objectives <p>The present study tested the acute effects of cannabis use on positive and negative affect in daily life and explored interactions with cannabis use disorder (CUD) symptoms, among 85 youth aged 15 to 24 years (<i>M</i> = 19.8, <i>SD</i> = 2.1; 41 females, 48%) during a 1-week pre-treatment monitoring period using autoregressive multilevel models with ecological momentary assessment data (observations = 1,570).</p> Results <p>Cannabis use was associated with increased positive affect and decreased negative affect after use. There was a significant quadratic lagged Positive Affect x Cannabis Use interaction, such that recent cannabis use was associated with greater positive affect specifically when previous moment positive affect was significantly lower- or higher-than-average positive affect levels. There was also a significant cross-level lagged quadratic Negative Affect x Cannabis Use x CUD severity interaction, such that recent cannabis use was associated with decreased negative affect specifically when previous moment negative affect was significantly lower- or higher-than-average negative affect levels, but most prominently among those with greater CUD symptoms.</p> Conclusions <p>The results support reinforcement models of cannabis use, suggesting that cannabis use may be both positively reinforcing generally, and negatively reinforcing for those with severe CUD.</p>