This study analyses the influence of children on female underemployment in Australia, by both (1) the age of the child(ren) and (2) the age of the youngest child. Furthermore, it examines educational attainment in determining female underemployment. The study utilises fixed effects models on 2001–2020 panel data based on the Household, Income and Labour Dynamics in Australia (HILDA) Survey to test relevant hypotheses on how the presence of children can impact the likelihood of female underemployment. While the presence of children significantly reduces the likelihood of reporting underemployment, results suggest that it is negatively related to the probability of female underemployment for children below 15 but positively associated with children 15 and above. This positive relationship with older children disappears only when restricted to the youngest child. Education matters once children are of school-going age: lower-educated mothers having children aged 5–14 are significantly less likely to be underemployed, whereas higher-educated mothers with children aged 15 and above are considerably more likely to be underemployed. The study contributes to the literature by exploring the age of the child(ren), the age of the youngest child and educational attainment in determining female underemployment.