We investigate the role of peer effects in the workplace on individual active transportation mode choices. We collect original data through an online survey on networks and sustainable behaviors among 334 individuals working in ten research laboratories at the University of Grenoble Alps in February 2020. We apply linear and nonlinear models of peer effects on active modal choice, untangling the role of conformism and strategic complementarity in social influence. We show that given our data, a linear local-average specification is the preferred empirical model of peer effects, and we estimate strong and significant endogenous peer effects.