Objective: The CoronabaBY study investigates the perceived pandemic burden, parenting stress, child and parent mental health problems as well as the utilization of psychosocial support measures in families with children between 0-3 years.Methods: Participants were recruited and surveyed via smartphone app for this cross-sectional study. Standardized questionnaires on perceived pandemic burden, parenting stress, parental symptoms of depression and anxiety, children`s regulatory or emotional and behavioral problems and utilization of early childhood intervention services were applied. Results: N = 991 parents (Mage = 33.7 years, 94% mothers, 92% German nationals) with infants (n = 554, Mage = 5.9 months) or toddlers (n = 435, Mage = 25.9 months) participated in the first half-year of 2021. 65% of the parents perceived a high pandemic burden, approx. 40% experienced elevated parenting stress and 24% showed symptoms of depression/anxiety. Infants and toddlers did not show increased mental health problems. 71% (62%) of the stressed (strongly stressed) parents were aware of early childhood intervention services, 36% (55%) were using them in the past and 5% (13%) at the time being.Conclusions: Families with infants and toddlers experience the pandemic as highly stressful. The main challenges are increased parental affective symptoms and limited resources for childcare due to parenting stress. Staggered detrimental effects on children`s mental health might occur if the stressful conditions persist. Accessibility to early childhood intervention services should be a top priority for policy makers.