Background: This study aimed to determine the efficacy of the risk of ovarian malignancy algorithm (ROMA), calculated using the carbohydrate antigen 125 (CA125) and human epididymis protein 4 (HE4) levels and the menopausal status, as a predictor of peritoneal dissemination in ovarian cancer. Methods: The CA125 and HE4 levels and the ROMA were compared between ovarian cancer patients (n = 122) with or without peritoneal dissemination. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated, and the results were compared with those of computed tomography (CT). Results: The CA125, HE4, and ROMA values differed significantly depending on the presence of peritoneal dissemination (p < 0.0001). The cut-off values were 181 U/ml for CA125, 161 pmol/ml for HE4, 44% for the ROMA (premenopausal), and 86% for the ROMA (postmenopausal). Among these markers, the ROMA (premenopausal) was the strongest predictor of peritoneal dissemination, with a specificity of 85.0% and a positive predictive value of 81.3%. In addition, the detection rates of small disseminations with less than 2 cm in diameter for the ROMA (93%) and HE4 (60%) were superior to that of CT (53%). Conclusions: The ROMA was a significant predictor of peritoneal dissemination and may be superior to CT for the detection of patients with small disseminations.