Objective To investigate the effect of social constraints on fear of cancer recurrence and the mediating role of illness perception and non-adaptive cognitive emotion regulation in patients receiving hematopoietic stem cell transplantation (HSCT). Methods A total of 232 HSCT patients were interviewed using the Social Constraints Scale, the Brief Illness Perception Questionnaire, the Cognitive Emotion Re-gulation Questionnaire and the Fear of Cancer Recurrence Inventory. Results The scores of fear of cancer recurrence was (13.92±5.28). More than half (50.86%) of patients had a high level of fear of cancer recurrence (P<0.05). The total indirect effect of social constraints on the fear of cancer recurrence was 0.140, in which the specific mediating effect of disease perception and non-adaptive cognitive emotion regulation strategies accounted for 10.22% and 10.59% respectively, and the chain mediating effect accounted for 5.20%. Conclusion Patients undergoing HSCT have a high level of fear of cancer recurrence. Illness perception and non-adaptive cognitive emotion regulation strategies play a chain mediating role between social constraints and fear of cancer recurrence. Nursing staff should pay attention to and take effective measures to reduce the social constraints of patients undergoing HSCT, reduce the negative illness perception, improve the non-adaptive cognitive emotion regulation strategy, and achieve the purpose of reducing the level of fear of cancer recurrence in patients undergoing HSCT.