Objective: To evaluate the impact of pharmaceutical care service in hypertensive patients in a Peruvian hospital, detecting and solving drug related problems (DRP) using Dáder method. Method: This prospective, quasi experimental, quali-quantitative study was focused in detection and solving drug related problems (DRP) and measuring outcomes of pharmaceutical care interventions in 94 patients from July 2010 to June 2011. Results: It was detected 139 DRP (1.47 DRP per patient). In the 139, 68 (48.9%) were of necessity, 50 (35.9%) were effective and 21 (15.2%) security. 92 (66.19%) of pharmacist interventions were accepted. Between interventions accepted, 72 (78.26%) contributed to solving DRP. Between interventions not accepted, 33 (70.21%) continued not solved. Conclusion: The results show the importance and usefulness of pharmaceutical care service for hypertensive patients attended ambulatory in a Peruvian Hospital.