Tackling poor mental health and wellbeing among healthcare workers remains a high priority for the National Health Service (NHS). This study evaluated the social value of the Coming to Our Senses mindfulness-based programme, designed to support the mental health of workers in high-stress medical environments, for NHS healthcare workers in Wales. Respondents (N = 39) to an online survey were assessed for mental health social value at baseline and one-month follow-up using the Short Warwick–Edinburgh Mental Wellbeing Scale (SWEMWBS) and the Social Value Bank (SVB). Social return on investment (SROI) ratios were calculated by dividing the change in mental health social value, health resource service use, and productivity costs by the programme delivery costs. Social value generated per respondent was £1890.05 using SWEMSWBS and £5775.97 using SVB. Cost savings in health resource and productivity were £9.41 and £79.10 per respondent, respectively. The programme delivery cost was £463.63 per respondent. Overall, including sensitivity analysis, the programme yielded a positive SROI of £2.35–£4.27:£1 using SWEMWBS or £6.82–£12.65:£1 using SVB. These findings suggest that the Coming to Our Senses programme may be effective in generating positive social value by improving self-reported mental health and wellbeing among NHS healthcare workers in Wales.