Retention of placenta (RP) is a failure of the fetal membrane to be expelled and remained from 8 to 48 hours, average 12 hours after parturition. There are a variety of risk factors for the occurrence of RP. So, the aim of this study was to quantify the relative risk of calving season, parity, and gestation length on the occurrence of RP, and assess the impact of RP on the subsequent reproductive parameters, and the economic losses. A data of 2940 purebred Holstein-Friesian cows were collected from reliable records of large commercial dairy farm, Sharkia governorate, Egypt. These cows calved during the period extended from January 2018 to December 2019. Cows that did not release the fetal membranes within the first 12 hours after calf expulsion were diagnosed with RP. Results of logistic regression analysis revealed that the important risk factors for the occurrence of RP were summer calving season and short gestation period. Odds ratio estimation for summer calving season compared to spring calving was 2.84. The probability of RP incidence in cows with shorter gestation period was 0.19 times more than cows with longer gestation length, and the total direct economic losses from RP was 47 $/cow. Finally, we can conclude that short gestation length and summer calving season are strongly correlated with the development of RP in dairy cows. Subsequently, the occurrence of RP significantly affects reproductive parameters resulting in economic losses in dairy herds.