Background Group sex is associated with increased risk of HIV and sexually transmissible infections (STIs), but there is limited data on group sex among female sex workers (FSW). Understanding current group sex practices among FSW may assist with understanding and addressing the rise in STIs observed among Australian FSW in the 2010s. The aim of this study was to examine the proportion of FSWs who had engaged in group sex. Methods: A cross-sectional survey was conducted among FSWs attending the Melbourne Sexual Health Centre, Australia, between March and April 2019. Females aged ≥18 years who self-reported as a sex worker were invited to participate in the survey asking whether they had had group sex in the past 3 months. Group sex was defined as sex that involved two or more sexual partners. Results: Of the 51 FSWs who completed the survey, the median age was 29 years (IQR 24–34). Almost half (49%; n = 25) reported having group sex in the past 3 months, with a median number of group sex events of two (IQR 1–4). Australian-born FSW were more likely to report group sex than overseas-born FSW (76% vs 42%; P = 0.02). Age, number of paid clients and injecting drug use were not associated with group sex. Conclusion: The present study findings show that group sex is common among FSW and should be included in peer sexual health education and interventions among FSW.