Background The aim of this prospective study was to assess the effectiveness of concentrated growth factors (CGF) in preventing the development of alveolar osteitis (AO) after the extraction of partially-erupted mandibular third molars. Methods Seventy patients (26 men and 44 women) 18 years or older (mean age 25.86; range 18-35) underwent 140 third molar extractions. All the patients presented with bilateral, partially-erupted mandibular third molars and underwent surgical extractions. In each case, one socket received CGF and the other served as a control. The predictor variable was the CGF application and the sides were categorized as 'CGF' and 'non-CGF'. The outcome variable was the development of AO during the first postoperative week. Other study variables included age and gender. Data were analyzed using Cochran's Q test with the significance level set at aPvalue less than 0.05. Results The overall frequency of AO was 11.4% for the control group. The frequency of AO in the CGF group was significantly lower than in the non-CGF group (p < 0.001). Conclusions Based on the results of this study, application of CGF fibrin gel may decrease the risk of AO development after mandibular third molar surgery.