This study examines the effectiveness of two modes of exercise on self-efficacy (SE) and exercise perception (EP) in adults with Down syndrome (DS). Thirteen participants attended four sessions: a baseline assessment, an Assisted Cycling Therapy (ACT) session, a resistance training (RT) session, and a session of no training (NT). In the baseline assessment, 1-repetition max (1RM) measurements and voluntary pedal rate measurements were taken. In the cycling intervention, the participant completed 30 minutes of assisted cycling at 35 percent greater than their voluntary pedaling rate. In the resistance training session, 2 sets of 8-12 repetitions of the leg press, chest press, seated row, leg curl, shoulder press, and latissimus pulldown were performed. During the session of no training, participants played board games with student researchers for 35 minutes.Two subsets of the Physical Activity and Self Efficacy Survey were administered prior to each session (i.e., pretest) and after the intervention (i.e., post-test). The results were consistent with the hypothesis that ACT would lead to higher SE than RT or NT. However, ACT did not lead to higher EP than RT or NT as hypothesized. Additionally, it was hypothesized that RT would lead to higher SE and EP than NT, but the results did not support this. In conclusion, an acute session of ACT demonstrated a significant trend for improved self-efficacy in adults with DS.