Older children with online schooling requirements, unsurprisingly, were reported to have increased screen time during the first COVID-19 lockdown in many countries. Here, we ask whether younger children with no similar online schooling requirements also had increased screen time during lockdown. We examined children’s screen time during the first COVID-19 lockdown in a large cohort (n = 2209) of 8-to-36-month-olds sampled from 15 labs across 12 countries. Caregivers reported that toddlers with no online schooling requirements were exposed to more screen time during lockdown than before lockdown. While this was exacerbated for countries with longer lockdowns, there was no evidence that the increase in screen time during lockdown was associated with socio-demographic variables, such as child age and socio-economic status (SES). However, screen time during lockdown was negatively associated with SES and positively associated with child age, caregiver screen time, and attitudes towards children’s screen time. The results highlight the impact of the COVID-19 lockdown on young children’s screen time.