Newly-hired engineers often counter feelings of uncertainty, confusion, shock and surprise in their first full-time employment after university graduation by engaging in socialization actions and processes. Generally, newcomers undergo socialization through two sets of socialization processes when they are hired into an organization: (1) initiating proactive behaviors and (2) participating in company-initiated actions, called organizational tactics. This thesis aims to provide a first look at the socialization environment among newcomer engineers in the U.S. aerospace and defense (A&D) industry. A comprehensive understanding is achieved by examining how newly- hired engineers at A&D organizations initiate proactive behaviors and participate in organizational tactics to adjust to their new jobs and organizations. Multiple regression analysis is used to examine the relationships that various processes have with socialization outcomes. Latent Profile Analyses (LPA) is employed to identify holistic profiles that best characterize newly hired engineers’ socialization processes and whether engineers with different types of profiles present varying socialization outcomes. The findings show that newcomer engineers heavily rely on socially- oriented socialization processes, and that newcomer engineers more frequently achieve socialization through organizational tactics rather than proactive behaviors. It is also revealed that newcomer engineers in the A&D industry generally require 8 months to achieve high levels of adjustment. Implications and recommendations for newcomers, organizations, and educational programs are discussed. The content of this thesis has been submitted for review to the International Journal of Engineering Education (IJEE).