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 learned 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 suitableβ = 0.436, p = 0.001; suitable vs. not suitableβ = 0.510, p < 0.001], knowledge (β = 0.298, p = 0.020), and professional specialty (military doctor vs. nonmilitary doctorβ = 0.198, p = 0.034) were found to be correlated with intention. However, attitude, subjective norms, and descriptive norms were determined to be nonsignificant 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.