AbstractGroup-level safety climate (GSC) is a recognized leading indicator of safety performance in the literature. However, there is limited understanding of the mechanisms through which multilevel (i.e., organizational, group, and individual) factors collectively influence GSC as promoted by general contractors in construction. A model is proposed to examine the interactions and causal relationships between four multilevel factors—organizational-level safety climate (OSC), coworker support (CS), supervisory safety-specific transformational leadership (SSTL), individual psychological capital (PsyCap)—and GSC. A two-wave online survey was conducted within a large contractor company in the US over 2 years. A total of 280 employees completed both surveys. The structural equation modeling analysis technique was adopted to test the hypotheses. The results show that OSC, CS, and supervisory SSTL significantly contribute to GSC. In addition, supervisory SSTL and CS positively affect individual PsyCap, and PsyCap positively moderates the relationship between supervisory SSTL and GSC. The study suggests that construction contractors should consider implementing leadership and PsyCap interventions to cultivate a positive GSC that potentially can lead to improved safety performance.