Objectives To use the extended theory of planned behaviour (TPB) to predict smoking cessation counsellors' intentions to offer smoking cessation support. Design Cross-sectional study Setting Taiwanese military Participants A survey of 432 smoking cessation counsellors was conducted in 2017. Primary and secondary outcome measures All participants completed a self-administered questionnaire that solicited information concerning demographics, smoking behaviour, self-rated suitability for being a counsellor, the knowledge and skills learnt from training courses and the TPB construct. Results The factors of perceived behavioural control (β=0.590, p<0.001), self-rated suitability for being a counsellor (acceptable vs not suitable, β=0.436, p=0.001; suitable vs not suitable, β=0.510, p<0.001), knowledge (β=0.298, p=0.020) and professional specialty (military doctor vs non-military doctor, β=0.198, p=0.034) were found to be correlated with intention. However, attitude, subjective norms and descriptive norms were determined to be non-significant correlates. The model explained 59.7% of the variance for the intention to offer smoking cessation support (F[12,343]=44.864, p<0.001). Conclusions To encourage smoking cessation counsellors to offer cessation support to smokers, policies should aim to increase their perceived behavioural control, knowledge and self-rated suitability for being a counsellor.