Background: Medication process is a powerful instrument for curing patients. Obeying the commands of this process has an important role in the treatment and provision of care to patients. Medication error, as a complicated process, can occur in any stage of this process, and to avoid it, appropriate decision-making, cognition, and performance of the hospital staff are needed. Objectives: The present study aimed at identifying and evaluating the nature and reasons of human errors in the medication process in a hospital using the extended CREAM method. Methods: This was a qualitative and cross-sectional study conducted in a hospital in Hamadan. In this study, first, the medication process was selected as a critical issue based on the opinions of experts, specialists, and experienced individuals in the nursing and medical departments. Then, the process was analyzed into relative steps and substeps using the method of HTA and was evaluated using extended CREAM technique considering the probability of human errors. Results: Based on the findings achieved through the basic CREAM method, the highest CFPt was in the step of medicine administration to patients (0.056). Moreover, the results revealed that the highest CFPt was in the substeps of calculating the dose of medicine and determining the method of prescription and identifying the patient (0.0796 and 0.0785, respectively). Also, the least CFPt was related to transcribing the prescribed medicine from file to worksheet of medicine (0.0106). Conclusions: Considering the critical consequences of human errors in the medication process, holding pharmacological retraining classes, using the principles of executing pharmaceutical orders, increasing medical personnel, reducing working overtime, organizing work shifts, and using error reporting systems are of paramount importance.