Background and Objective: Streptococcal pharyngitis is one of the most common bacterial infections that its improper treatment could lead to complications such as heart and kidney problems. Although streptococcal pharyngitis makes up a low percentage of pharyngitis etiology, penicillin derivatives are prescribed for many of the patients with pharyngitis. The aim of this study was to determine the prevalence of streptococcal infection in pharyngitis patients treated with penicillin derivatives as well as their drug resistance patterns. Materials and Methods: This cross-sectional trial was performed on 437 patients aged between 1-90 years with pharyngitis admitted to the emergency ward and treated with penicillin derivatives. A throat swab for culture and smear preparation for group A beta hemolytic streptococus was done for each patient, followed by evaluation of antibiotic resistance to group A hemolytic streptococci. Results: From a total of 437 patients diagnosed with streptoccocal pharyngitis, only 31 patients (7.09%) turned up positive for group A beta hemolytic streptococci. Drug resistancy to Erythromycin 38.2%, Gentamicin 58.8% and Penicillin 2.9% were reported. Conclusion: Considering the fact that 7.09% of the patients required antibiotic therapy, the irrational consumption of antibiotics likely leads to an increased likelihood of drug resistance or allergy. This issue deserves special attention in the continuing educational programs for physicians.