OBJECTIVE: To determine whether a standardised and manualised care intervention in men in primary care could achieve superior improvement of lower urinary tract symptoms (LUTS) compared with usual care. DESIGN: Cluster randomised controlled trial. SETTING: 30 National Health Service general practice sites in England. PARTICIPANTS: Sites were randomised 1:1 to the intervention and control arms. 1077 men (≥18 years) with bothersome LUTS recruited between June 2018 and August 2019: 524 were assigned to the intervention arm (n=17 sites) and 553 were assigned to the usual care arm (n=13 sites). INTERVENTION: Standardised information booklet developed with patient and expert input, providing guidance on conservative and lifestyle interventions for LUTS in men. After assessment of urinary symptoms (manualised element), general practice nurses and healthcare assistants or research nurses directed participants to relevant sections of the manual and provided contact over 12 weeks to assist with adherence. MAIN OUTCOME MEASURES: The primary outcome was patient reported International Prostate Symptom Score (IPSS) measured 12 months after participants had consented to take part in the study. The target reduction of 2.0 points on which the study was powered reflects the minimal clinically important difference where baseline IPSS is <20. Secondary outcomes were patient reported quality of life, urinary symptoms and perception of LUTS, hospital referrals, and adverse events. The primary intention-to-treat analysis included 887 participants (82% of those recruited) and used a mixed effects multilevel linear regression model adjusted for site level variables used in the randomisation and baseline scores. RESULTS: Participants in the intervention arm had a lower mean IPSS at 12 months (adjusted mean difference -1.81 points, 95% confidence interval -2.66 to -0.95) indicating less severe urinary symptoms than those in the usual care arm. LUTS specific quality of life, incontinence, and perception of LUTS also improved more in the intervention arm than usual care arm at 12 months. The proportion of urology referrals (intervention 7.3%, usual care 7.9%) and adverse events (intervention seven events, usual care eight events) were comparable between the arms. CONCLUSIONS: A standardised and manualised intervention in primary care showed a sustained reduction in LUTS in men at 12 months. The mean difference of -1.81 points (95% confidence interval -0.95 to -2.66) on the IPSS was less than the predefined target reduction of 2.0 points. TRIAL REGISTRATION: ISRCTN Registry ISRCTN11669964.