Background <p>A previously conducted study reported that insomnia rates among oncology patients in Ireland are twice that of the general population, and that a breast cancer diagnosis was an independent predictor for clinical insomnia disorder. The aim of this study is to explore this interaction further in a larger cohort of breast cancer patients.</p> Methods <p>We evaluated sleep disturbance and sleep hygiene practices among adult breast cancer patients via questionnaires. Sociodemographic data, clinical characteristics, sleep history and attitudes towards sleep assessments were collected and analysed.</p> Results <p>The comprehensive 40-item questionnaire was completed by 315 patients. Of this cohort, 56% reported a change in their sleeping patterns since their cancer diagnosis, with over 55% of the study population having sub-threshold or clinical insomnia disorder. Although 64.2% of patients believed that questions regarding sleep should be part of breast cancer assessment, only 32% recalled being asked about sleep by a healthcare worker. Moreover, only 27.1% of respondents felt their sleeping difficulties were adequately dealt with since their diagnosis.</p> Conclusion <p>In summary, sleep disturbance is prevalent among breast cancer patients. Despite a majority of breast cancer patients recognising the importance of sleep assessment, a significant gap remains in healthcare providers addressing these concerns effectively.</p>