Objectives: Understanding how to promote rewarding exercise experiences is important for attempts to help individuals be physically active. This qualitative study aimed to investigate the optimal psychological states experienced during rewarding exercise activities. Specifically, participants were interviewed as soon as possible after recent, rewarding exercise experiences in order to maximise detail and accuracy of recall. Design: Event-focused qualitative study. Method: A sample of 18 individuals (Mage= 32.94 years) participated in event-focused, semi-structured interviews soon after a rewarding exercise experience (M = 2 days later). Data were analysed thematically, while strategies were employed to enhance trustworthiness. Results: Participants reported two distinct optimal experiences during rewarding exercise activities, matching descriptions of flow and clutch states. Flow occurred in contexts involving exploration, novelty/variation, and flexible outcomes, while the experience was described as enjoyable at the time, and involved lower perceived effort. Clutch states occurred in contexts involving achievement and pressure. Exercisers perceived clutch states to be enjoyable afterwards but not at the time, and to involve intense effort. Notable differences were apparent in the outcomes of each state in that flow had an energising effect, whereas clutch states were fatiguing. Conclusions: This study presents evidence for flow and clutch states in exercise, supporting emerging research in sport. These findings provide insights into the occurrence, experience, and outcomes of flow and clutch states specifically from the exerciser's perspective. Such insights can inform future research on flow and clutch states in this setting, and may provide strategies for reliably inducing each state during exercise.