This study examined adolescents' interest in aerobic fitness testing and its relation to the test performances. Adolescents (N = 356) from three middle schools participated in the study. The participants took two aerobic fitness tests: the Progressive Aerobic Cardiovascular Endurance Run (PACER) and One-Mile Run (1MR) with a two-day interval, and completed two interest scales immediately after each test. Test performances, interest, and body mass index data were collected. Data were analyzed using descriptive statistics, multivariate analysis of variance/covariance, and hierarchical regression analyses. Student situational and personal interests were low-to-moderate overall in both aerobic fitness tests. Boys reported significantly higher situational interest than girls, but there was no gender difference in personal interest. Personal interest was a significant predictor for PACER (b = 0.27) and 1MR (b = -0.37). The predictability of situational interest to testing performances varied between PACER and 1MR. PACER and 1MR might have rendered distinct motivational stimuli that led to the varied predicting power of situational interest.