PurposeThe individual placement and support (IPS) model of supported employment is a leading evidence-based practice in community mental health services. In Japan, individualized supported employment that is highly informed by the philosophy of the IPS model has been implemented. While there is a body of evidence demonstrating the association between program fidelity and the proportion of participants gaining competitive employment, the association between fidelity and a wider set of vocational and individual outcomes has received limited investigation. This study aimed to assess whether high-fidelity individualized supported employment programs were superior to low-fidelity programs in terms of vocational outcomes, preferred job acquisition, and patient-reported outcome measures (PROMs).MethodsA prospective longitudinal study with 24-month follow-up analyzed 16 individualized supported employment programs. The Japanese version of the individualized Supported Employment Fidelity scale (JiSEF) was used to assess the structural quality of supported employment programs (scores: low-fidelity program, ≤ 90; high-fidelity program, ≥ 91). Job acquisition, work tenure, work earnings, job preference matching (e.g., occupation type, salary, and illness disclosure), and PROMs such as the INSPIRE and WHO-Five Well-being index were compared between groups.ResultsThere were 75 and 127 participants in the low-fidelity group (k = 6) and high-fidelity group (k = 10), respectively. The high-fidelity group demonstrated better vocational outcomes than the low-fidelity group, i.e., higher competitive job acquisition (71.7% versus 38.7%, respectively, adjusted odds ratio (aOR) = 3.6, p = 0.002), longer work tenure (adjusted mean difference = 140.8, p < 0.001), and better match for illness disclosure preference (92.6% versus 68.0%, respectively, aOR = 5.9, p = 0.003). However, we found no differences between groups in other preference matches or PROM outcomes.ConclusionHigh-fidelity individualized supported employment programs resulted in good vocational outcomes in a real-world setting. However, enhancing service quality to increase desired job acquisition and improve PROMs will be important in the future.Clinical Trial RegistrationUMIN000025648