Background <p>Work and sleep mutually influence one another: adequate sleep supports cognitive functioning and social regulation at work, whereas safe and respectful working conditions facilitate recovery and sleep. Although workplace bullying has been proposed as an important work-related determinant of sleep problems, the empirical base has been dominated by cross-sectional research, with comparatively few longitudinal studies. Furthermore, the mechanisms underlying this association, as well as the potential reverse association, remain poorly understood.</p> Methods <p>Using a large longitudinal national probability sample of the Swedish workforce (<i>N</i> = 2,024), the present study examined how exposure to bullying is associated with sleep problems, and whether sleep problems, in turn, increase vulnerability to subsequent bullying, in both directions through cognitive and behavioural mechanisms, and how these processes depend on the work environment.</p> Results <p>Exposure to bullying was indirectly related to subsequent sleep problems via increased brooding, with this pathway most pronounced in seemingly safe work environments. In the reversed direction, sleep problems were indirectly related to later exposure to bullying via brooding and conflict involvement; the brooding pathway was evident only in more hostile work environments, whereas the conflict involvement pathway operated across levels of hostile work climate.</p> Conclusions <p>Taken together, the findings indicate that the relationship between bullying and sleep is neither simple nor uniformly reciprocal. Instead, different work environments intensify risk in different directions, highlighting the importance of cognitive sense-making processes and organizational context in understanding when and how bullying and sleep problems become intertwined.</p>