The mental healthcare sector wants to prescribe outdoor therapies, but as yet lacks outdoor capabilities. The tourism sector has those capabilities, but as yet has not shown therapeutic outcomes. Here, therefore, I reanalyse previously published qualitative datasets, to examine mental health effects perceived by outdoor tourists. Outcomes indicate that nature, eco and adventure tourism enterprises could potentially become certified providers of prescribable outdoor therapies in mainstream healthcare. This represents a large economic opportunity, significantly greater than current investment in outdoor education and recreation. From a healthcare perspective, the analysis presented here provides proof of concept only: clinical testing and medical certification are still required. From a tourism perspective, it indicates an opportunity to apply existing skills, under a different commercial model. From a tourism research perspective, it demonstrates a need for more rigorous research on mental health outcomes, beyond emotional experiences.