As newcomers transition into new organizational settings, organizational insiders serve as important information and social support resources to help newcomers adapt to their new work environments. In this study, I develop and test a model showing how newcomers develop their communication networks over time, and revealing how this dynamic aspect of the newcomer socialization process may facilitate newcomer adjustment and success in the workplace. I conduct a three-wave longitudinal study within the first 28 weeks of employment and find that institutionalized socialization tactics, task interdependence, and proactive personality partially help newcomers form their communication networks. Second, I find that newcomers' communication networks facilitate newcomer adjustment but only at time 2 (week 16) and time 3 (week 28). Third, findings only marginally support the proposition that newcomers' communication networks mediate the relationships between proactive personality and task mastery. However, newcomers' communication networks did not mediate the relationships between other two socialization factors - institutionalized socialization tactics and task interdependence - and newcomer adjustment. Fourth, findings generally support the proposition that newcomer adjustment predicts intrinsic career success. The post hoc analysis indicates that newcomer adjustment mediates the relationships between socialization factors and career success. Last, findings fail to support the proposition that socialization factors explain how quickly newcomers develop their communication networks. However, the preliminary results show that communication networks develop during the very early entry period.