Temper tantrums during toddlerhood are common behaviours and are seen as a normal part of emotional development. However, the mechanisms explaining the severity of toddler tantrums have not been studied much. This longitudinal study aims to examine the bidirectional associations between parenting discipline techniques (i.e., ignoring, power assertion, and consistency) and the severity of tantrums (a combination of duration and intensity). In total, 99 parents responded and 97 dyads participated in the observational task (55 boys and 42 girls). There were 96 observations at T1 (mean age of children = 29.97 months, ranged from 18 to 43 months; 55 boys and 41 girls), 92 observations at T2, and 89 observations at T3. Observational data on temper tantrum behaviours has been collected using a parent-child standardized observational clean-up task and temper tantrum behaviours were coded. Temper tantrum severity will be computed from the coded temper tantrum behaviours: the duration was defined as the number of ...