OBJECTIVE We analyzed growth rates of benign ovarian serous cystadenomas and cystadenofibromas to understand what percentage would show a volume doubling time (DT) of less than 3 years, between 3 and 5 years, or greater than 5 years. METHODS We retrospectively reviewed pathology records (January 1, 2014, to June 30, 2019) to find all surgically excised ovarian serous cystadenomas and cystadenofibromas. Imaging records were then reviewed to identify those that had been confidently identified with ultrasound imaging, magnetic resonance imaging, or computed tomography at least twice before surgical removal, with at least a 60-day interval between studies. Three orthogonal measurements were recorded on the first and last imaging studies on which the mass was detected, with volume calculations by the prolate formula (product of 3 measurements multiplied by 0.52). The volume DT was calculated and grouped into 1 of 5 categories: (1) DT of less than 1 year; (2) DT of 1 to 3 years; (3) DT of 3 to 5 years; (4) DT of 5 to 10 years; and (5) no growth (any mass with a DT >10 years or showing a decrease in volume). RESULTS A total of 102 of 536 cystadenomas and 44 of 227 cystadenofibromas met inclusion criteria. Of the 146 tumors, 40 (27.4%) had a DT of less than 1 year; 38 (26.0%) had a DT of 1 to 3 years; 22 (15.1%) had a DT of 3 to 5 years; 10 (6.8%) had a DT of 5 to 10 years; and 36 (24.7%) showed no growth. CONCLUSIONS A total of 53.4% of ovarian serous cystadenomas/cystadenofibromas have a DT of less than 3 years; 15.1% have a DT between 3 and 5 years; and 31.5% have a DT of greater than 5 years or show no growth.