Purpose This study further approaches the role of estrogen-related receptors (ERRs) in ovarian cancer. Protein expression of ERR alpha, ERR beta and ERR gamma in ovarian cancer was assessed and was correlated with ovarian cancer markers, steroid hormone receptors and cancer-associated genes. Additionally, we examined to what extent expression of ERRs affects survival of ovarian cancer patients. Methods For this purpose, we established a tissue microarray from 208 ovarian cancer patients and performed immunohistochemical analyses of the mentioned proteins. Results ERR alpha and ERR gamma protein could be detected at different levels in more than 90% of all ovarian cancer tissues, whereas expression of ERR beta was observed in 82.2% of the cases. ERR alpha was found to positively correlate with ovarian cancer marker CEA (p < 0.005) and ERR gamma correlated with ER alpha (p < 0.001). Univariate survival analyses revealed that ERR alpha expression did not affect overall (OS) or progression-free survival (PFS) of ovarian cancer patients. In contrast, higher expression of ERR beta in serous ovarian cancers was found to lead to a significantly decreased OS (p < 0.05). The strongest impact on survival was exhibited by ERR gamma. Lower expression of this receptor in women with serous ovarian cancers indicated significantly increased OS compared to those with higher levels of ERR gamma (p < 0.05). Multivariate survival analyses revealed ERR gamma as an independent prognostic marker regarding OS of patients with serous ovarian cancer. Conclusion Our data demonstrating that ERR proteins are frequently expressed in ovarian cancer and high levels of ERR beta and ERR gamma significantly decreased OS of serous ovarian cancer patients suggest that these proteins might be interesting therapy targets in this cancer entity.