Organizational veterans and external stakeholders such as clients often play an important and informal role in newcomer socialization, influencing newcomer cognition and behavior and providing learning opportunities and social support that facilitate employee adjustment and performance enhancement. However, from a sensemaking perspective, newcomers may also draw insight from stakeholder behavior in order to better understand how to best meet job-related objectives and expectations. These understandings may manifest as performance-related motives, leading to the adoption of risky behaviors that can be detrimental to newcomer health and organizational effectiveness. Using multisource, multilevel, and longitudinal data, we demonstrate that the alcohol use norms of both organizational veterans and clients are significantly associated with the performance drinking motives of newcomers in sales and client service teams, suggesting that veteran and client norms signal to newcomers that drinking alcohol is an effective and legitimate means to improve job performance. In addition, we demonstrate that performance drinking motives mediate the positive relationship between veteran and client alcohol use norms and newcomers' frequency of work-based heavy drinking. Finally, we find that the frequency of work-based heavy drinking is positively related to newcomer alcohol misuse and mediates the positive relationship between performance drinking motives and newcomer alcohol misuse.