ObjectivesThe purpose of the current study is to test the efficacy of the Proactivity Orientation Program (POP) in facilitating university freshmen's proactive socialization. Design/SettingA longitudinal field experiment was designed to test the hypotheses. Based on action regulation theory, the 8-h POP included training on developing goals, collecting information, generating and executing plans, and processing feedback. ParticipantsA total of 148 freshmen from a comprehensive university in China were randomly assigned to a control group (N = 74) or an experimental POP intervention group (N = 74). Main outcome measuresQuestionnaires regarding four proactive socialization behaviors (i.e., feedback seeking, relationship building with instructors, general socializing, and positive framing), social integration, and anxiety were administered. The Office of Educational Administration provided freshmen's GPAs for the first semester. ResultsCompared with those in the control group, freshmen in the POP group (a) reported more proactive socialization behaviors (i.e., feedback seeking, relationship building with instructors, general socializing, and positive framing), (b) experienced higher levels of social integration and lower levels of anxiety in the first three and four months after entering the university, and (c) had better academic performance for the first semester. Proactive socialization behaviors were found to mediate the POP's treatment effects on some of the adjustment outcomes. Furthermore, the intervention effects of the POP did not materialize immediately, but rather, emerged over time. ConclusionsThe findings provide preliminary support for the POP intervention in facilitating freshmen's proactive socialization behaviors and adjustment outcomes. Our findings also suggest the importance of proactivity for freshmen adjustment and academic success.