Background: Primary care doctors are responsible to provide smoking cessation intervention (SCI) to smokers in a community. This study aimed to assess the SCI practice among primary care doctors themselves and its associated factors. Methods: This cross-sectional study was conducted from July to October 2016. All the 140 doctors in 12 public primary care clinics in Kuala Lumpur were invited to participate in this study. However, only 122 doctors (females, 82.8%) completed the self-administered questionnaire that assessed their demography, clinical experience, SCI practice and its barriers, self-efficacy in delivering and knowledge on smoking and SCI. Results: Only 42.6% of the doctors had good SCI practice. Almost all doctors assessed the smoking status of their patients (98.4%) and advised them to quit (98.4%). However, lesser proportions of the doctors followed up the practice of patients (50.0%), taught smokers on various methods of quit smoking (46.70%) and discussed about the barriers and resources to quit prior to the quit date (27.9%). Less than one-fourth of the doctors were confident in providing SCI. Although 69.7% had previous training in SCI, many felt they had inadequate knowledge (56.6%) and skills (47.5%). Only 11.5% of doctors thought their previous training was enough. Having higher level of knowledge on smoking and SCI was significantly associated with good SCI practice [adjusted Odds Ratio (95% Confidence Intervals): 1.21 (1.02, 1.43), p=0.026]. Conclusion: The SCI practiced by the primary care doctors in this study was sub-standard, particularly in assisting smokers to quit and arranging follow up. Low self-efficacy in providing SCI was also common. These inadequacies may be due to poor knowledge and skills, which needs to be improved through effective clinical training.