Background Few European smokers receive professional counselling when attempting to quit smoking, resulting in suboptimal success rates and poor health outcomes. Healthcare providers in general practice play an important role in referring smokers to smoking cessation counselling. We chose the Netherlands as a case study to qualitatively explore which factors play a role among healthcare providers in general practice with regard to referral for smoking cessation counselling organised both inside and outside general practice. Methods We conducted four focus groups and 18 telephone interviews, with a total of 31 healthcare providers who work in general practice. Qualitative content analysis was used to identify relevant factors related to referral behaviours, and each factor was linked to one of the three main components of the COM-B behaviour model (i.e., capability, opportunity and motivation) as well as the six sub-components of the model. Results Dutch healthcare providers in general practice typically refer smokers who want to quit to counselling inside their own general practice without actively discussing other counselling options, indicating a lack of shared decision making. The analysis showed that factors linked to the COM-B main components 'capability' and 'opportunity', such as healthcare providers' skills and patients' preferences, play a role in whether patients are referred to counselling inside general practice. Factors linked to all three COM-B components were found to play a role in referrals to counselling outside general practice. These included (knowledge of) the availability and quality of counselling in the region, patients' requests, reimbursement, and sense of urgency to refer. The identified factors can both act as barriers and facilitators. Conclusions The findings of this research suggest that more smokers can be reached with smoking cessation counselling if implementation interventions focus on: (i) equipping healthcare providers with the knowledge and skills needed to refer patients; (ii) creating more opportunities for healthcare providers to refer patients (e.g., by improving the availability and reimbursement of counselling options); and (iii) motivating healthcare providers to discuss different counselling options with patients.