Purpose: This study aimed to examine the effect of peer presence on session rating of perceived exertion (RPE) responses. Method: Fourteen males, with mean (SD) age 22.4 (3.9) years, peak oxygen uptake 48.0 (6.6) mL·kg−1·min−1, and peak power output 330 (44) W, completed an incremental cycling test and 3 identical experimental sessions, in groups of 4 or 5. Experimental sessions involved 24 minutes of cycling, whereby the work rate alternated between 40% and 70% peak power output every 3 minutes. During cycling, heart rate was collected every 3 minutes, and session-RPE was recorded 10 minutes after cycling, in 3 communication contexts: in written form unaccompanied (intrapersonal communication), verbally by the researcher only (interpersonal communication), and in the presence of the training group. Session-RPE was analyzed using ordinal regression and heart rate using a linear mixed-effects model, with models fit in a Bayesian framework. Results: Session-RPE was voted higher when collected in the group’s presence compared with when written (odds ratio = 4.26, 95% credible interval = 1.27–14.73). On average, the posterior probability that session-RPE was higher in the group setting than when written was .53. Session-RPE was not different between the group and verbal, or verbal and written collection contexts. Conclusions: This study suggests that contextual psychosocial inputs influence session-RPE and highlights the importance of session-RPE users controlling the measurement environment when collecting votes.