Contribution: This study explores the direct relationships between campus environment, personality traits, engineering self-efficacy, academic performance, and psychological well-being of engineering undergraduates, and the indirect relationships between them with engineering self-efficacy as mediator which had not been studied previously in a developing country context. The findings of this research guide policy makers to improve engineering education while considering these factors. Background: Engineering education plays a significant role in enhancing the quality of engineers. Personality traits, campus environment, and engineering self-efficacy could potentially impact the academic performance and psychological well-being of engineering undergraduates. An indirect relationship exists between these dimensions with engineering self-efficacy acting as a mediator. Research Questions: 1) Do campus environment, personality traits, and engineering self-efficacy significantly impact the academic performance of engineering undergraduates? 2) Do campus environment, personality traits, and engineering self-efficacy significantly impact the psychological well-being of engineering undergraduates? and 3) Does engineering self-efficacy mediate the indirect relationships between campus environment, personality traits, academic performance, and psychological well-being of engineering undergraduates? Methodology: The research participants were 1005 engineering undergraduates from 16 universities of Pakistan. Structural equation modeling (SEM) was used to assess the hypothesized relationships between personality traits, campus environment, engineering self-efficacy, academic performance, and psychological well-being. Findings: Personality traits and engineering self-efficacy significantly impact academic performance. Campus environment does not impact academic performance. Campus environment, personality traits, and engineering self-efficacy significantly impact psychological well-being. Campus environment and personality traits significantly impact engineering self-efficacy. Engineering self-efficacy mediates the relationship between the variables being studied.