Study Objectives: Work-family conflict is a threat to healthy sleep behaviors among employees. This study aimed to examine how Work-to-Family Conflict (demands from work that interfere with one's family/personal life; WTFC) and Family-to-Work Conflict (demands from family/personal life that interfere with work; FTWC) are associated with several dimensions of sleep among information technology workers. Methods: Employees at a U.S. IT firm (n = 799) provided self-reports of sleep sufficiency (feeling rested upon waking), sleep quality, and sleep maintenance insomnia symptoms (waking up in the middle of the night or early morning) in the last month. They also provided a week of actigraphy for nighttime sleep duration, napping, sleep timing, and a novel sleep inconsistency measure. Analyses adjusted for work conditions (job demands, decision authority, schedule control, and family-supportive supervisor behavior), and household and sociodemographic characteristics. Results: Employees who experienced higher WTFC reported less sleep sufficiency, poorer sleep quality, and more insomnia symptoms. Higher WTFC also predicted shorter nighttime sleep duration, greater likelihood of napping, and longer nap duration. Furthermore, higher WTFC was linked to greater inconsistency of nighttime sleep duration and sleep clock times, whereas higher FTWC was associated with more rigidity of sleep timing mostly driven by wake time. Conclusions: Results highlight the unique associations of WTFC/FTWC with employee sleep independent of other work conditions and household and sociodemographic characteristics. Our novel methodological approach demonstrates differential associations of WTFC and FTWC with inconsistency of sleep timing. Given the strong associations between WTFC and poor sleep, future research should focus on reducing WTFC.