An inverse relationship has been suggested to exist between affect and exercise intensity. As a consequence, adherence to high-intensity exercise is posited to be lower than moderate-intensity exercise, although no study to date has prospectively assessed this hypothesis using objective measures of exercise behaviour. This trial examined the affective response to moderate-intensity continuous training (MICT; n= 14) and high-intensity interval training (HIIT; n = 16) in 30 previously inactive adults (Mage = 51), and its utility to predict exercise adherence 1- and 6-months after a 10-day intervention. Affect was assessed at 25%, 50%, 75% and 100% of workout completed during each exercise session using the feeling scale (FS). FS scores taken at the midpoint of all exercise sessions were averaged for analyses. Participants wore accelerometers for 7 consecutive days at baseline, 1-, and 6-months. As expected, affect was significantly higher in MICT (M = 2.7), as compared to HIIT (M = 1.5; p = 0.01, ?2 = 0.2). Affect did not change significantly over the 10 days of training (p = 0.4, ?2 = .04), and there was no condition x time interaction (p = 0.33, ?2 = 0.04). Affect failed to predict exercise behaviour at 1-month (ÃŸ = -0.01; p = 0.97, AdjR2 = -0.04) and 6-month (ÃŸ = -0.25, p = 0.25, AdjR2 = 0.02) follow-ups. These findings contradict the popular notion that in-task affect predicts future exercise behaviour, and is the first study to prospectively examine the relationship between affect and adherence using objective measures.