Background <p>Biosecurity is critical to prevent the introduction and spread of pathogens within and between layer farms. External biosecurity seeks to prevent pathogen entry or exit, while internal biosecurity focuses on limiting the spread of pathogens within the farm. Effective biosecurity practices not only safeguard animal health but also improve productivity, welfare, and sustainability in general. This study examines the temporal trends in biosecurity scores in Irish layer farms from 2020 to 2023, at national level and per farm type, using the Biocheck.UGent tool. The study highlights the progress achieved and the key areas requiring improvement. Data from 133 layer farms were analysed, along with recommendations made to improve biosecurity by the private veterinary practitioners.</p> Results <p>Biosecurity scores improved over the study period. Internal biosecurity scores were higher (range = 68-83) than external scores (range = 86-90). Farms assessed at least two times showed improved external and total scores, with an increase of 4 points in the median. Despite frequent recommendations for improvement, categories management of entrance of staff and visitors consistently received low scores. When comparing biosecurity between production systems in layer farms, barn systems had higher scores (external = 82, internal = 90) than free-range (80, 77) and enriched colony systems (75, 88).</p> Conclusions <p>The findings highlight the need for improving biosecurity compliance, particularly in areas consistently showing low scores, such as management of entrance of visitors and farm workers and infrastructure and biological vectors. More support should be provided to farmers to enhance these areas.</p>