Abstract:  Adverse drug reactions (ADRs) are a frequent cause for hospitalization and occur often in hospitalized patients. The objective of this study was to establish an ADR reporting and monitoring system at a teaching hospital. The pharmacovigilance unit of Masih Daneshvari hospital was established by a clinical pharmacist and a clinical pharmacologist. Healthcare professionals were encouraged to report any suspected ADRs encountered in in‐patients. The incidence, pattern, seriousness, severity and preventability of the reported ADRs were analysed. During the period of 12 months, for 6840 patients, 112 spontaneous reports were received. The most frequently reported reactions were due to anti‐infective agents (58.2%). Ceftriaxone accounted for the highest number of the reported ADRs among anti‐infective agents. The skin and appendages system was the most frequently affected system (32.5% of all reactions). Seventeen per cent of the ADRs were reported as serious reactions. Although the incidence of ADRs reported by physicians and nurses was found to be low, this programme was useful as a preliminary programme in initiating a culture of ADR reporting among healthcare professionals. Improved communication between the physicians and nurses with the pharmacovigilance centre in the hospital is suggested.