Objective: To explore general practitioners’ (GPs) and primary care nurses’ perceived barriers to raising the topic of weight in general practice. Design: A qualitative study using the Theoretical Domains Framework (TDF). 34 semistructured interviews were conducted to explore views, opinions and experiences of initiating a discussion about weight. Content and thematic analyses were used to analyse the interview transcripts. Setting: General practices located in one primary care trust in the South West of England. Participants: 17 GPs and 17 nurses aged between 32 and 66 years. The modal age range for GPs was 30–39 years and for nurses, 40–49 years. Results: Barriers were synthesised into three main themes: (1) limited understanding about obesity care, (2) concern about negative consequences, and (3) having time and resources to raise a sensitive topic. Most barriers were related to raising the topic in more routine settings, rather than when dealing with an associated medical condition. GPs were particularly worried about damaging their relationship with patients and emphasised the need to follow their patient's agenda. Conclusions: Uncertainty about obesity, concerns about alienating patients and feeling unable to raise the topic within the constraints of a 10 min consultation, is adding to the reluctance of GPs and nurses to broach the topic of weight. Addressing these concerns through training or by providing evidence of effective interventions that are feasible to deliver within consultations may lead to greater practitioner engagement and willingness to raise the topic.