<p>Flow experience is often labeled as optimal experience or being in the zone. One research goal is to better understand the antecedents of flow to ultimately identify ways to increase it in interventions. We present a theoretical approach that considers task meaningfulness—the extent to which a certain task is perceived as personally meaningful—as a crucial antecedent of flow experience. We tested this proposition in a controlled experimental setting by having participants play Tetris and in everyday life by conducting a five-day ambulatory assessment study (both studies were preregistered; total <i>N</i> = 1,062). In the experimental setting, task meaningfulness had a causal and positive impact on flow experience. In everyday life, both constructs were positively associated across various situational contexts, even when controlling for skills-demands fit—the most established antecedent of flow. Our findings suggested that task meaningfulness and skills-demands fit were differentially associated with the experiential dimensions of flow. Task meaningfulness was more strongly related to the flow dimensions of absorption and intrinsic reward, whereas skill-demands fit showed a closer association with effort-less control. Crucially, our findings consistently demonstrated that task meaningfulness and the intrinsic reward dimension of flow constitute distinct constructs, thereby mitigating concerns of circular reasoning in our theoretical rationale, empirical evidence, and conclusions. Overall, we provide internally and externally valid evidence that task meaningfulness is a relevant yet previously overlooked antecedent of flow, offering a foundation for innovative and effective flow interventions.</p>