Aim To examine the effects of a transtheoretical model‐based WeChat health education programme on self‐management in haemodialysis patients in China. Design A longitudinal experimental intervention study. Methods Patients (N = 120) who underwent haemodialysis from December 2015–November 2017 were recruited and randomly allocated to either group 1 (who received a 3‐month WeChat health education immediately after randomization) or group 2 (who was combined with group 1 and received the same intervention at the 5th month after enrolment in the study). Self‐management, knowledge and self‐efficacy were assessed at baseline (T0), 3 months after enrolment in the study (T1), 21 months after enrolment in the study (T2). Results There were significant group effects on self‐efficacy; time effects on partnership, self‐care, emotion management with total self‐management; interaction effects on problem‐solving and emotion management within total self‐management according to the two‐way repeated measures ANCOVA. Further between‐group comparisons indicated that patients in group 1 had better self‐management than those in group 2 at T1. Within‐group comparisons demonstrated that, compared with the baseline values, group 1 had significantly improved self‐management at T1; however, group 2 had improved self‐management at T2. Conclusion The transtheoretical model‐based WeChat health education programme had a potentially positive effect on improving the self‐management of haemodialysis patients. Impact Self‐management is often difficult yet crucial for haemodialysis patients. This study indicated that the transtheoretical model‐based WeChat health education resulted in improved self‐management in haemodialysis patients and can be implemented in continuing care during the interdialysis period to improve self‐management in patients. Trial registration: ChiCTR1800018172.