Orientation training plays a crucial role in the process of newcomer socialization by equipping employees with the knowledge, abilities, and skills necessary for success in a new work setting. However, relatively few studies have investigated orientation training from a socialization perspective and addressed its underlying mechanisms. To address this issue, we developed a model to elucidate the socialization process of newly hired salespersons undergoing skill-based orientation training. The model includes training reactions, two learning outcomes (learning engagement and skill acquisition), as well as two distal socialization outcomes (retention status and annual sales performance). Using a one-year multiperiod design, we conducted a multilevel analysis on data of 1184 new salesperson records nested in 37 off-site classes, which was obtained from a US pharmaceutical company operating in China. The results revealed that newcomers' reactions to orientation training were positively associated with their learning engagement and skill acquisition, which in turn resulted in a higher newcomer retention ratio. Furthermore, skill acquisition was found to be a significant mediator between training reactions and newcomers' annual sales performance. By combining self-report, trainer-report and objective indicators, this study provides a new and compelling evidence on how orientation training accelerates newcomer socialization success.