This study identifies five core building blocks of a mentally healthy workplace: leadership, connectedness, safety, work design, and capability. Using data from nearly 10,000 workers, it shows that wellbeing is shaped by everyday workplace experiences, not standalone initiatives. The findings highlight that different industries face different challenges, so approaches need to be tailored rather than one-size-fits-all. Importantly, the research shifts the conversation from simply preventing harm to actively creating environments where people can thrive, offering a more practical and measurable way to approach workplace mental health.