Introduction: Adverse drug reactions (ADR) are caused by a wide range of drugs including antibiotics. Currently, the prevalence and pattern of antibiotic-related ADR in Saudi Arabia are not well reported. The present study aimed to evaluate the ADR pattern caused by antibiotics in a tertiary healthcare center.Methods: This was a retrospective study conducted on 85 patients admitted to tertiary care hospital medical wards during the period from 2015 to 2019. The following data such as patient demographics (age, gender, weight, height), reason for admission, number of antibiotics use, comorbid condition, antibiotic(s) involved in ADR, classification of ADR, and type of ADR were recorded. Naranjo’s scale was used to measure the probability of ADR.Results: Among the 85 patients, the most frequent type of antibiotic was cephalosporins in 36.47%, followed by penicillins in 31.76% of the patients. The major type of ADR was rash (52.95%), followed by anaphylaxis reactions (10.59%) of the patients. Based on the Naranjo scale, the ADR was possible in 80% and probable in 18.82% of the cases. The presence of medical conditions displayed a significant association with the development of rashes (p=0.03). In addition, the female gender (p=0.009) and the presence of medical conditions (p=0.03) showed significant association with the development of anaphylaxis.Conclusion: Cephalosporin and penicillins were the most common antibiotics responsible for ADR, and the rash was the most common ADR.