BACKGROUND: Ensuring diversity in clinical trials can be a challenge, which may be exacerbated when recruiting vulnerable populations, such as participants with mental health illness. As recruitment continues to be the major cause of trial delays, researchers are turning to online recruitment strategies, e.g. social media, to reach a wider population and reduce recruitment time and costs. There is mixed evidence for the use of online recruitment strategies; therefore, the REcruitment in Mental health trials: broadening the 'net', opportunities for INclusivity through online methoDs (RE-MIND) study aimed to identify evidence and provide guidance for use of online strategies in recruitment to mental health trials, with a focus on whether online strategies can enhance inclusivity. This commentary, as part of the RE-MIND study, focusses on providing recommendations for recruitment strategy selection in future research with the aim to improve trial efficiency. A mixed-methods approach was employed involving three work packages: (I) an evidence review of a cohort of 97 recently published randomised controlled trials/feasibility or pilot studies in mental health to assess the impact of online versus offline recruitment; (II) a qualitative study investigating the experiences of n = 23 key stakeholders on use of an online recruitment approach in mental health clinical trials; (III) combining the results of WP1 and WP2 to produce recommendations on the use of an online recruitment strategy in mental health clinical trials. The findings from WP1 and 2 have been published elsewhere; this commentary represents the results of the third work package. CONCLUSION: For external validity, clinical trial participants should reflect the populations that will ultimately receive the interventions being tested, if proven effective. To guide researchers on their options for inclusive recruitment strategies, we have developed a list of considerations and practical recommendations on how to maximise the use of online recruitment methods.