Sclerosing peritonitis is an uncommon condition that has been reported in patients with luteinized ovarian thecomas, although some pathologists have suggested that the underlying ovarian pathology is not always neoplastic. We now report sclerosing peritonitis in a patient with an uncommon, luteinized variant of an adult granulosa cell tumor. To the best of our knowledge, this association has not been described previously. We suggest that sclerosing peritonitis may result from the release of substances by luteinized ovarian stromal cells, in the context of hyperplasia or neoplasia, which stimulate the proliferation of submesothelial fibroblasts.