Objective To examine the time course and predictors of fear of cancer recurrence (FCR) in breast cancer survivors over a period of 18 months after initial surgery. Methods Breast cancer patients (n = 267) were followed until 18 months after primary breast surgery. Shortly after surgery, participants completed the Life Orientation Test‐Revised to measure optimism and the Concerns about Recurrence Scale to measure FCR. Mixed regression analysis was performed with age, optimism, marital status, education, type of surgery, with or without lymphectomy, chemotherapy, hormonal therapy, or radiotherapy, time since surgery, and all interactions with time as predictors of FCR. Results The final model included a significant interaction between age and time since surgery and a main effect for optimism. Conclusion These results suggest that the course of FCR depends on the age of breast cancer survivors. Younger survivors showed an increase of fear during the first 1.5 years after breast surgery, whereas older survivors showed stable levels during the first 6 months after which it declined. Also, less optimistic survivors reported higher levels of FCR. Health care providers should pay (extra) attention to FCR in younger and less optimistic patients and offer psychological help when needed.