The Family Doctor Concept (FDC) programme was introduced to public primary care clinics in late 2013 as part of the reform agenda in the primary healthcare delivery system. The study aimed to develop a validated and reliable instrument to evaluate the FDC implementation fidelity in primary care clinics. The instrument, which adapted the concept of patient-centred care (PCC), resulted from a series of expert discussions, a literature search, an FDC guideline, and a review of meeting minutes. A 2-step process was conducted with experts to achieve content and face validity. Consequently, the instrument was piloted in 5 public primary care clinics in Selangor involving 8 trained raters. Inter-rater reliability was estimated using intraclass correlation (ICC), while internal consistency was measured using Kuder-Richardson Formula 20 (KR-20). The final instrument comprises 3 sections (instructions, clinic's characteristics and assessment items), with Section 3 containing 15 items divided into four components - population registration, formation of a primary care team, integrated treatment, and monitoring and evaluation. The ICC for total score was excellent, 0.981, while the ICCs of the individual component scores were good to excellent (population registration: 0.937, formation of primary care team: 0.742, integrated treatment: 0.996, and monitoring and evaluation: 0.996). The value of KR-20 was 0.615, which was considered adequate. The instrument developed was found to be valid in terms of face and content validity and reliable in measuring the fidelity of FDC implementation with excellent inter-rater reliability.