Separate streams of organizational socialization research have recognized the importance of (a) newcomer proactivity and (b) manager support in facilitating newcomer adjustment. However, extant research has largely focused on the newcomers’ experience, leaving the perspectives of managers during socialization relatively unexplored—a theoretical gap that has implications both for newcomer adjustment and manager-newcomer interactions that may serve as a basis for future relationship development. Drawing from the “interlocked” employee behavior argument of Weick (1979), we propose that managers’ perception of newcomers’ proactive behaviors are associated with concordant manager behaviors, which, in turn, support newcomer adjustment. Further, we investigate a cognitive mechanism—managers’ evaluation of newcomers’ commitment to adjust—which we expect underlies the proposed relationship between newcomers’ proactive behaviors and managers’ supportive behaviors. Using a time-lagged, 4-phase data collection of a sample of new software engineers in India and their managers, we were able to test our hypothesized model as well as rule out alternative explanations via multilevel structural equation modeling. Results broadly supported our model even after controlling for manager-newcomer social exchange relationship, proactive personalities of both newcomers and managers, and potential effects of coworker information providing. The implications of our findings for theory and practice are discussed.