Background and Aim: Subcutaneous administration may result in complications such as bruising and pain at the injection site. This study was performed as in order to determine the effect of cold application and compression on pain and bruising in subcutaneous heparin injection. Methods: The study was a randomized controlled trial. 72 patients were included in the study. Each patient in the sample was both experimental (cold and compression) and control groups and 3 different parts of abdomen were used for injection of each patient. The data of the research were collected by using Patient Identification Form, Subcutaneous Heparin Observation Form and Visual Analog Scale (VAS). Results: In the study, it was observed that after heparin injection, ecchymosis developed in 16.4%, 28.8%, and 54.8% of the patients, respectively, and pain was experienced during injection in 12.3%, 43.5%, and 44.2% of the patients, respectively, on the pressure, cold application, and control site groups, and this difference was statistically significant (p<0.001). Conclusion: In the study, it was found that bruising size of the compression group was smaller in contrast with the other groups. When the VAS mean was examined for the groups, it was found that the patients in the compression group had lower pain than the other groups. In order to prevent complications that may arise in nurses' subcutaneous heparin injections and to increase the quality of patient care, it may be recommended to transfer the 60-second compression application after subcutaneous heparin applications to clinical applications and to conduct studies comparing compression and cold application with other applications for future studies.