Context: The Balance Error Scoring System (BESS) is the most commonly used balance test during concussion assessment; however, the test has known limitations related to fatigue. Jumping and landing along with running are common athletic activities that adversely affect postural control. However, the effect of neither subexertional running nor jumping and landing tasks on the BESS is known. Therefore, the purpose of this study was to investigate the effects of a brief exercise bout of running or jumping on BESS performance. Design: We recruited 52 recreationally active participants who were divided into 3 groups: (1) Drop Jump (Landing), Treadmill Running (Run), and Control. Methods: All participants performed a preintervention BESS test and were then randomly assigned to a group. The jumping group performed 10 drop jumps from a 50 cm box, 30 seconds between trials, the running group performed a 3-minute treadmill run, and the control group sat quietly for 5 minutes. All participants then completed a second BESS test. The primary analysis was a 2 (time) by 3 (group) repeated-measure analysis of variance with sex as a covariate. Results: There was a significant interaction (F = 7.396, P = .002). On post hoc, there was a significant improvement (lower) score in the Control group (PRE: 13.9 [4.5]; POST: 10.5 [2.9]; P = .019, d = 0.89) but no significant differences in either the running (P = .579) or landing (P = .849) groups. Conclusions: A relatively brief exercise intervention resulted in participants failing to improve a subsequent BESS assessment, whereas control participants who rested for 5 minutes committed fewer (3.4) errors. These results suggest that sports health care providers should recognize that even low- to moderate-intensity brief exercise can result in a failure to improve with repeat BESS administration.