Objectives To investigate how peer dynamics, specifically interpersonal conversations between a potential offender and a peer, contemporaneous with a crime opportunity, influence perceptions of sanction certainty and social costs. Methods Data are analyzed from randomized experiments and hypothetical vignettes embedded within a nationwide, online survey ( n = 1,275). Vignettes were presented for three distinct crime opportunities, drunk driving, fighting, and insurance fraud. Results The findings suggest that respondents adjust two core decision-making perceptions—the perceived certainty of being legally sanctioned and perceived social costs such as stigma or embarrassment—in accord with the content of verbal communications from peers. There is evidence for this both between and within subjects. Conclusions The study underscores the importance of accounting for both physical and social features of the situational context for crime in models of offender decision making. Implications are drawn regarding the social milieu for offender decision making, and the broader criminological relevance of choice principles.