The construction industry is vital to New Zealand's economy, accounting for 6.7% of the GDP. Regrettably, mental health concerns have long plagued this sector, yet little research on the mental well-being of construction workers has been conducted in the country. A comprehensive analysis was undertaken to identify factors that impact the mental health of construction employees to address this gap. The study utilized a systematic literature review (SLR) following the PRISMA guidelines, identifying 50 papers meeting the inclusion criteria. Additionally, semi-structured interviews were conducted with construction professionals and labourers to compare and analyze the findings. The results showed that the factors identified through the interviews closely aligned with those uncovered through the SLR. Notably, adherence to Council regulations was found to impact the mental health of construction professionals, while poor physical environments, such as heavy precipitation, were consistently highlighted by both professionals and workers. These findings can be used to formulate effective strategies to enhance the mental well-being of construction workers and provide insights for future studies on the mental health of construction employees in New Zealand.