Environmental temperatures potentially influence reproductive performance and sexual selection by restricting opportunities for activity. However, explicit tests of the behavioral mechanisms linking thermal variation to mating and reproductive performance are rare. We address this gap in a temperate lizard by combining social network analysis with molecular pedigree reconstruction in a large-scale thermal manipulation experiment. Populations exposed to cool thermal regimes presented fewer high activity days compared to populations exposed to a warmer regime. While plasticity in thermal activity responses in males masked overall differences in activity levels, prolonged restriction nevertheless affected the timing and consistency of male-female interactions. Females were less capable than males of compensating for lost activity time under cold stress, and less active females in this group were significantly less likely to reproduce. While sex-biased activity suppression appeared to limit male mating rates, this did not correspond to a heightened intensity of sexual selection or shifts in the targets of sexual selection. In many populations facing thermal activity restriction, sexual selection on males may play a limited role relative to other thermal performance traits in facilitating adaptation.