Previous studies have compared the effectiveness of dinoprost and cloprostenol in cows yielding conflicting results. The aim of our study was to evaluate the efficacy of single treatment with cloprostenol or dinoprost on estrus and reproductive performance in cows with unobserved estrus after service. The study was conducted over four years in two dairy herds of Polish Holstein Frisian cows under a herd health program with an average milk yield per cow over 9000 L. Cows (n=523) diagnosed ultrasonographically as non-pregnant and with a corpus luteum were randomly assigned to be treated with either cloprostenol (n=261) or dinoprost (n=262). The estrus detection rates after administration of cloprostenol or dinoprost were 59.4%, and 57.6%, respectively. The difference between both groups was not statistically significant (p>0.05). Distribution of observed estrus did not differ between cloprostenol and dinoprost. There were no differences (p>0.05) between cloprostenol and dinoprost in conception rate (65.2% vs. 66.2%, respectively) and pregnancy rate (57.5% vs. 54.9%, respectively). Mean days open were similar in cows of both treatments (177.5 ± 74.6 days vs. 175.8 ± 62.6 days, respectively; p>0.05). In conclusion, data from this study showed no significant differences in estrus detection rates and fertility between cows with unobserved estrus after service treated with cloprostenol or dinoprost. Both products are equally useful for the treatment of non-pregnant dairy cows with anestrus after service within a reproductive herd health program.