Integration of health services has been pursued worldwide. Diversity in integration approaches and in the contexts in which integrated programmes operate, however, hinders comparative analysis of care integration in both high-income countries (HICs) and low- and middle-income countries (LMICs). This study evaluates an HIC programme implemented in a delivery system resembling those of LMICs, especially its weak primary care system. The programme, Taiwan’s Family Doctor Plan (FDP), targets high-cost and chronic patients, incorporating key elements of integrated care, viz., case management, multidisciplinary teams and care pathways. This study estimates the effects of shifting from usual to integrated care and locates contextual factors that may distort programme implementation. To estimate programme effects, difference-in-differences analysis is applied to a balanced panel comprising >160 000 patients over 2009–13. Because physician participation is voluntary, a propensity score matching method is used to match providers. The research findings reveal that introduction of the FDP has not reoriented the model of care from fragmented towards integrated health services. It reduces continuity of care and has no effect on co-ordination of care. Regarding quality of care, the FDP is shown to have no effect on avoidable admissions and increases drug injections and emergency department visits. Several contextual factors may serve as barriers that impede elements of FDP from generating desirable outcomes. These include absence of registration and gatekeeping systems; limited capacities of clinics; and preponderance of fee-for-service remuneration. These findings suggest that HIC design elements may not be directly transferrable to settings with weak primary care systems, as is typical of LMIC healthcare. Changes at the system level, such as establishing regular sources of care, may be necessary before elements of integrated care are introduced to a weaker primary care system.