Background Parents’ belief in the effectiveness of physical punishment increases its use and influences children’s emotional and behavioural outcomes. This study explored the factors associated with parents’ beliefs regarding physical punishment of children aged 5–14 years in Bangladesh. Methods Data from 19,675 respondents in the Bangladesh Multiple Indicator Cluster Survey (MICS) 2019 were analysed. Socio-demographic variables were included as key exposures, and parental beliefs regarding child physical punishment served as the outcome variable. Associations were assessed using Chi-square tests, and significant predictors were identified through binary logistic regression analysis. Results The findings indicated that 34.57% of parents endorsed physical punishment as a means of ensuring proper upbringing. Significant predictors of this belief included the child’s age, sex, region, education level, household wealth quintile, mother’s education, and number of children. Parents of children aged 10–14 years were significantly less likely to believe physically punishing children compared with those aged 5–9 years (aOR: 0.91; 95% CI: 0.84–0.98). Similarly, parents of female children were less likely to believe in physical punishment compared to parents of male children (aOR: 0.89; 95% CI: 0.84–0.95). In contrast, parents were more likely to believe that children with functional difficulties needed physical punishment, with 47% higher odds compared to children without such difficulties (aOR: 1.47; 95% CI: 1.31–1.64). Conclusions Child physical punishment is common in Bangladesh, with many parents considering it necessary for proper child-rearing. Policymakers should take necessary initiatives to change parents’/caregivers’ point of view regarding child physical punishment, with giving priority to vulnerable groups.