The use of mobile technology for work purposes during family time has been found to affect employees’ work and family lives. Using a matched sample of 344 job incumbents and their spouses, we examined the role of mobile device (MD) use for work during family time in the job incumbent–spouse relationship and how this MD use crosses over to affect the spouse’s work life. Integrating the work–home resources model with family systems theory, we found that as job incumbents engage in MD use for work during family time, work-to-family conflict increases, as does the combined experience of relationship tension between job incumbents and spouses. This tension serves as a crossover mechanism, which then contributes to spouses’ experience of family-to-work conflict and, subsequently, family spills over to work outcomes for the spouse in the form of reduced job satisfaction and performance.