Background: The use of the Nurse-Led Mobile App (NL-Mapp) is a current and important option for educating patients about the symptoms that may arise from breast cancer surgery.

Introduction: Given the precise information and counseling services offered to breast cancer patients, NL-Mapp is considered an appropriate choice to support postoperative self-care.

Methods: This quasi-experimental study aimed to determine the impact of NL-Mapp on breast cancer patients after surgery. The study included 45 patients in the intervention group and 45 patients in the control group. First, NL-Mapp was developed by the research team. Patients were then taught how to use the app to manage their symptoms after breast cancer surgery, and online counseling was provided for patients' questions. The intervention started before surgery, and follow-up visits were made before discharge and in the first month.

Inclusion Criteria:

• Speaking the national language,
• The presence of primary breast cancer,
• The utilization of a smartphone for a minimum of one year,
• An age of 20 years

Exclusion Criteria:

• An uncontrollable medical problem,
• Having speech problems,
• Having hearing problems,
• Vision impairment,
• A psychiatric diagnosis/ongoing treatment
• Previous treatment due to a different type of cancer
• Rheumatological diseases,
• Fractures,
• Health problems leading to joint limitation,
• Amputation