We draw upon and extend socialization resources theory to explain how organizational newcomers leverage their social capital resources (i.e., vertical access and horizontal tie strength within their communication networks) and personal resources (i.e., core self‐evaluations) to learn about and assimilate into their work and organizations. The findings of a multiwave study of organizational entrants in China reveal the synergistic effects of relational and personal resources for newcomer adjustment. Newcomers learn and assimilate effectively not only when they have vertical connections to high‐status organization members but also when they can compensate for their lack of high‐status connections by leveraging their strong horizontal ties with peers and favorable core self‐evaluations. These findings provide a practical perspective on how to tailor newcomer onboarding practices to facilitate effective newcomer adjustment.