Abstract Introduction The research on sleep in the social-psychological domain is sparse. Gordon and colleagues (Gordon, Mendes, & Prather, 2017) proposed a bidirectional relationship between sleep and social processes. The current research tests this model in the military by examining the relationship between subjective sleep quality and an important social cognitive process in the contexts of military teams - psychological safety (i.e., an individual’s perceptions of interpersonal threat in their work environment; Edmondson, 1999). Methods One hundred and twenty-eight U.S. Army tank crewmen were surveyed prior to (T1), and immediately after (T2), participating in a two-week simulated combat training exercise. Each survey included the seven-item Insomnia Severity Index (ISI; Bastien et al., 2001), which served as a measure of subjective sleep quality (SSQ), and Edmonson’s seven-item Psychological Safety Questionnaire which measured team psychological safety (TPS). A cross-lagged panel model tested the effects of SSQ and TPS over the course of the training. Results Both SSQ and TPS were stable over the two time points, SSQT1: M=2.83, SD=.85, α=.83; SSQT2: M=2.63, SD=.83, α=.83; B=.387, SE=.08, β=.397, p<.001, and TPST1: M=3.7, SD=.72, α=.79; TPST2: M=3.67, SD=.75, α=.77; B=.619, SE=.07, β=.600, p<.001, respectively. Although SSQ and TPS were weakly related to one another at both time points, rT1=.122, p=.086 and rT2=.171, p = .028, only the cross-lagged path between SSQT1 predicting TPST2 was significant, B=.129, SE=.06, β=.147, p=.038. The cross-lagged path between TPST1 predicting SSQT2 was not significant, B=-.098, SE=.094, β=-.086, p=.296. Approximately 40% of the variance in CPS, R2=.4 as opposed to 17% in SSQ, R2=.17, was accounted for by the predictors in the model. Conclusion These results provide support for a directional (vs bidirectional) link between SSQ and TPS, insomuch that, in the context of military training, SSQ influences TPS, as opposed to the other way around. Elucidating the directionality of this relationship is not only important for advancing theory, but more importantly, it helps practitioners develop programs and policies that precisely address the right mechanism at the right time to maximize team effectiveness and wellbeing. Support This work was supported by the Military Operational Medicine Research Program (MOMRP).