Narratives describing firstâhand experiences of recovery from mental health problems are widely available. Emerging evidence suggests that engaging with mental health recovery narratives can benefit people experiencing mental health problems, but no randomized controlled trial has been conducted as yet. We developed the Narrative Experiences Online (NEON) Intervention, a web application providing selfâguided and recommender systems access to a collection of recorded mental health recovery narratives (n=659). We investigated whether NEON Intervention access benefited adults experiencing nonâpsychotic mental health problems by conducting a pragmatic parallelâgroup randomized trial, with usual care as control condition. The primary endpoint was quality of life at week 52 assessed by the Manchester Short Assessment (MANSA). Secondary outcomes were psychological distress, hope, selfâefficacy, and meaning in life at week 52. Between March 9, 2020 and March 26, 2021, we recruited 1,023 participants from across England (the target based on power analysis was 994), of whom 827 (80.8%) identified as White British, 811 (79.3%) were female, 586 (57.3%) were employed, and 272 (26.6%) were unemployed. Their mean age was 38.4±13.6 years. Mood and/or anxiety disorders (N=626, 61.2%) and stressârelated disorders (N=152, 14.9%) were the most common mental health problems. At week 52, our intentionâtoâtreat analysis found a significant baselineâadjusted difference of 0.13 (95% CI: 0.01â0.26, p=0.041) in the MANSA score between the intervention and control groups, corresponding to a mean change of 1.56 scale points per participant, which indicates that the intervention increased quality of life. We also detected a significant baselineâadjusted difference of 0.22 (95% CI: 0.05â0.40, p=0.014) between the groups in the score on the âpresence of meaningâ subscale of the Meaning in Life Questionnaire, corresponding to a mean change of 1.1 scale points per participant. We found an incremental gain of 0.0142 qualityâadjusted life years (QALYs) (95% credible interval: 0.0059 to 0.0226) and a ÂŁ178 incremental increase in cost (95% credible interval: âÂŁ154 to ÂŁ455) per participant, generating an incremental costâeffectiveness ratio of ÂŁ12,526 per QALY compared with usual care. This was lower than the ÂŁ20,000 per QALY threshold used by the National Health Service in England, indicating that the intervention would be a costâeffective use of health service resources. In the subgroup analysis including participants who had used specialist mental health services at baseline, the intervention both reduced cost (âÂŁ98, 95% credible interval: âÂŁ606 to ÂŁ309) and improved QALYs (0.0165, 95% credible interval: 0.0057 to 0.0273) per participant as compared to usual care. We conclude that the NEON Intervention is an effective and costâeffective new intervention for people experiencing nonâpsychotic mental health problems.