ObjectiveCOVID-19 significantly contributed to an increase in psychological distress and may have disproportionally impacted certain sociodemographic groups. This study aimed to assess the prevalence of psychological distress among Australian adults aged 18–64 years and identify sociodemographic factors associated with psychological distress during the COVID-19 pandemic. MethodsSecondary analyses were conducted using data from the National Health Survey 2020–21 to calculate weighted national estimates of the prevalence of psychological distress using the Kessler Psychological Distress scale (K10). The association between sociodemographic factors and psychological distress was analysed using multivariable logistic regression, with adjustments for complex survey design. ResultsThe average of K10 score was 16.94, with a prevalence of combined high/very high distress reported at 21.13 % among Australian adults. Young women aged 18–25 reported the highest average scores (M = 20.44) across all sex and age groups. Risk factors associated with psychological distress included lower personal income, marital status (never married; widowed/divorced/separated) and being ‘born in Australia’. Protective factors included homeownership and having children in the household. Additionally, among women, being aged ≥56 was significantly associated with lower odds of psychological distress. LimitationsData collection relied on self-completed online form, and a cross-sectional design limits the inference of a causal relationship. DiscussionDuring COVID-19 pandemic, lower personal income and being female have consistently been identified as risk factors for psychological distress. Targeted and tailored interventions based on age, sex and disadvantage are warranted, particularly focusing on younger women, to alleviate the adverse effect of the pandemic on the population's mental health.