The majority of literature on the work-family interface has focused on, and provided evidence of, the conflict associated with engagement in both work and family roles (Eby, Casper, Lockwood, Bordeaux, & Brinley, 2005). Research examining the positive aspects of work and family participation remains limited. The current study investigated how work-family positive spillover is transferred between members of the supervisor-employee dyad and subsequently how this affects employee sleep outcomes. It was hypothesized that work-to-family affective positive spillover experienced by supervisors would crossover to employees and increase their experiences of work-to-family affective positive spillover. In turn, this would allow for better employee sleep. It was also proposed that these relationships would depend on the level of employee perceptions of family-supportive supervisor behaviors (FSSB), such that higher levels of FSSB would result in higher levels of employee positive spillover and better employee sleep. As part of a larger study, survey data were collected in a sample of 696 workers supervised by 180 managers in the information technology sector. Contrary to expectations, results indicated that supervisor positive spillover was negatively related to employee positive spillover. Furthermore, FSSB moderated the association between supervisor positive spillover and employee sleep duration, such that the relationship between supervisor positive spillover and employee sleep duration was positive under high levels of FSSB, but negative under low levels of FSSB. Again, this finding was contrary to expectations. Alternative explanations are discussed.