Background <p>Temper tantrums are among the most common behavioral problems reported by parents, with significant consequences for child and family well-being. While previous research has linked the quantity of center-based childcare to several externalizing behaviors in young children, little is known about its association with temper tantrums.</p> Objective <p>We hypothesized that higher childcare quantity is associated with more frequent and longer tantrums in toddlers and preschoolers. Given that age serves as a proxy for developmental maturation in child behavior, we expected these associations to diminish as children grow older.</p> Methods <p>We examined 602 reports of parents with children 1–5&#xa0;years old (<i>M</i> = 34.13&#xa0;months, 51.83% boys). Statistically controlling for sex, age, vocabulary, and socioeconomic status of the child, we first examined tantrum frequency and duration in children attending center-based childcare compared to those not attending. Then, we tested for the relationship between time in childcare and tantrum frequency/duration. Finally, we allowed for an interaction between time and children’s age.</p> Results <p>Ordinal regression analyses revealed that, above and beyond attendance, toddlers and preschoolers spending more time in center-based childcare throw more frequent and longer temper tantrums than those spending less time. This effect does not depend on their age though.</p> Conclusions <p>Although significant, the association between childcare quantity and tantrum frequency/duration was weak in this study. Yet, even small increases in tantrumming may accumulate over time and affect certain groups of children and families, highlighting childcare as one of multiple factors shaping children’s irritability across toddlerhood and preschool years.</p>