This article examines the determinants of the gender gap in multiple job holding in Australia using all 18 waves (2001–2018) of the Household, Income and Labour Dynamics in Australia (HILDA) survey. In Australia, like most high‐income countries, the multiple job holding rate is higher for women compared with men. The empirical analysis focuses on the role played by factors such as wage rates, hours worked, household wealth, job security, education, demographics and demand conditions. Probit regressions point to a large, negative and highly statistically significant effect of hours worked in the primary job on the probability of holding a secondary job. This effect is larger (more negative) for women. A decomposition analysis suggests that a large share of gender gap in multiple job holding (c. 90 per cent) may be attributed to the gender gap in the hours worked in the primary job. Regulation concerning working time can be expected to affect multiple job holding rates.