Aim The aim of this study was to determine the factors affecting the behaviour of regular physical activity in patients with hypertension using the health action process approach (HAPA) model. Design This cross‐sectional study was conducted on 176 hypertension patients, in Astaneh‐e‐Ashrafiyeh, Guilan, Iran, 2018–2019. Methods Data collection tools included demographic characteristics, medical history, the short form of International Physical Activity Questionnaire (IPAQ) and scales related to the HAPA model. The data were analysed using chi‐square, independent t test, one‐way ANOVA, Pearson's correlation coefficient and path analysis on AMOS, version 23.0. Results Action self‐efficacy ( β = 0.59), outcome expectancy ( β = 0.20) and risk perception ( β = 0.18) had a statistically significant effect on intention. Moreover, the path coefficient between intention ( β = 0.35) and coping self‐efficacy ( β = 0.29) with physical activity was statistically significant. The results revealed that HAPA constructs were able to describe 45% of the variance in intention and 31% of the variance in physical activity behaviour. Conclusion The HAPA model is a useful framework for describing the factors affecting physical activity in hypertension patients.