We aimed to compare the results of image-guided drainage in addition to antibiotic therapy (antibiotherapy) with antibiotherapy alone in the treatment of tubo-ovarian abscesses (TOAs) and evaluate C-reactive protein (CRP) levels in predicting the success of antibiotherapy. This was a retrospective study of 194 patients hospitalized with TOA. Patients were divided into the following two groups: those who underwent image-guided drainage in addition to parenteral antibiotherapy and those who did not undergo image-guided drainage and received antibiotherapy alone. CRP levels on the day of admission (day 0), day 4 of hospitalization (day 4), and day of discharge (last day) were recorded. The percentage of decrease in CRP levels during day 4 and the last day compared with that on day 0 was calculated. A total of 106 patients (54.6%) underwent image-guided drainage with antibiotherapy, whereas 88 patients (45.4%) did not undergo drainage and received antibiotherapy alone. At admission, the mean CRP level was 203.4 (± 96.7)mg/L and was similar in both groups. The mean decrease in the CRP level on day 4 compared with that on day 0 was 48.5% and was statistically higher in the group that underwent image-guided drainage. Antibiotherapy failed in 18 patients, and a statistically significant difference was observed between treatment failure and the rate of decrease in the CRP level on day 4 compared with that on day 0. According to the receiver operating characteristic (ROC) analysis, if the CRP level measured on day 4 decreased by < 37.1% compared with that on day 0, the probability of treatment failure would increase (area under the curve = 0.755; 95% confidence interval, 0.668-0.841; sensitivity, 73.6%; specificity, 60%). Image-guided drainage combined with antibiotherapy in the treatment of TOA has high success rates, lower recurrence rates, and lower surgical requirement, and the mean decrease in the CRP level on day 4 can be monitored at treatment follow-up. In patients receiving antibiotherapy alone, if the CRP level on day 4 decreases by < 37.1%, the treatment protocol should be changed.