Background <p> Schizophrenia is a chronic and disabling mental disorder that leads to poor social functioning, low quality of life, and a heavy burden for families and society. In China, service engagement among community-dwelling patients remains insufficient, limiting the effectiveness of treatment and rehabilitation. Existing engagement-focused interventions were developed and evaluated primarily in high-income countries, leaving little evidence for low- and middle-income settings, including China. This study describes the protocol of a randomized controlled trial designed to evaluate the effectiveness and cost-effectiveness of a community-based service engagement intervention for young adults with schizophrenia in China.</p> Methods <p> A single-blind, individually randomized controlled trial will be conducted in community health service centers in Yangpu District, Shanghai, recruiting 192 eligible patients with schizophrenia. Participants will be randomized 1:1 to the intervention or control group. The intervention consists of six individual sessions and three group sessions over three months, focusing on medical-social support, peer-social support, and service engagement facilitation. Primary outcomes include service engagement, attitudes, and health behaviors; secondary outcomes include recovery, symptoms, quality of life, and costs. Data will be analyzed under the intention-to-treat principle using difference-in-differences models, with multiple imputation for missing values. Cost-effectiveness analysis will include direct and indirect costs reported by patients and caregivers.</p> Discussion <p> This trial is among the first in China to evaluate a community intervention for improving service engagement in schizophrenia. If shown to be effective and cost-effective, the program could be scaled up within existing community-based rehabilitation systems, offering practical guidance for policymakers and practitioners to enhance recovery, promote social inclusion, and reduce the burden of care.</p> Trial registration <p>Chinese Clinical Trial Registry (ChiCTR2500113435). Registered, 2025. </p>