Sleep disturbances are a risk factor for poorer lifestyle behaviours. While PCOS is associated with a higher prevalence of sleep disturbances, the relationship between sleep and lifestyle behaviours is unknown in PCOS. Self-reported data from the Australian Longitudinal Study on Women’s Health young cohort (31–36 years, n=6067, n=464 PCOS, n=5603 non-PCOS) were collected on PCOS, anthropometry, physical activity, sedentary behaviour, diet (74-item validated food frequency questionnaire) and sleeping behaviour (sleep quantity and adverse sleep symptoms). Multivariate regression models controlled for sleeping behaviour, BMI, age, marital status, education, income and area of residence. Women with PCOS reported greater adverse sleep symptoms, higher energy intake, diet quality (dietary guidelines index (DGI)), fibre intake and sedentary time and lower glycaemic index, compared to women without PCOS. This was not maintained for energy intake and sedentary behaviour on adjustment for confounders. For diet quality, there was an interaction between PCOS and sleep disturbances. Only for women with fewer sleep disturbances (~8 hours sleep/no adverse sleep symptoms) was PCOS associated with better diet quality (DGI higher by 3.14±0.86, p<0.001), with no differences in diet quality for women with poorer sleep. Lifestyle behaviours in women with PCOS appear to be influenced by sleep quality and quantity.