Using data collected during the COVID-19 pandemic from 28,185 families with preschoolers living in Hubei, China, this study examined the relationship between home quarantine duration and preschoolers' sleep problems. In particular, we tested the potential mediating role of child screen usage time and the potential moderating role of real interpersonal interactions in the family setting. Results indicated that home quarantine duration was positively associated with preschoolers' sleep problems indirectly through both types of screen time. More importantly, a conditional indirect pathway was identified, such that home quarantine duration was linked with preschoolers' more sleep problems through longer traditional screen time only when real interpersonal interactions were relatively low. These findings, reveal some potential intervention targets and avenues, such as setting limits on child screen time and enhancing more real family interpersonal interactions, to help parents of young children successfully navigate the challenges during home quarantine during the pandemic.