Abstract: The aim of this study was to determine the effect of urea as silage additive on the fermentation parameters and dry matter losses of grape pomace silages. Grape pomace (Vitis vinifera L.) Pinot Gris variety with 45 % dry matter content was ensilaged in laboratory conditions. Grape pomace was ensilaged in two variants: without additive as a control and with addition of urea applied at a rate of 4kg.t-1. Mini silo bags were filled by grape pomace matter from both variants and hermetically sealed. The mini silo bags were stored in air-conditioned laboratory conditions (t 22±1 °C). Average samples from each variant (n=3) were taken for laboratory analysis after 5 weeks of storage. Dry matter was analysed after drying of the sample at (103±2 °C). Content of lactic, acetic and butyric acid on analyzer EA 100 (Villa Labeco, SR) by ionic electrophoresis method was determined. Contents of alcohols were detected by Conway microdiffusion method and active acidity by the electrometric method. For evaluation of statistical parameters SPSS Statistics 20.0 (IBM) (ANOVA-Tukey test) were used. Dry matter losses in control silages 19.1% and in silages with urea 11.2% (P<0.05) were observed. After addition of urea a significantly (P<0.05) higher lactic acid content in grape pomace silages in comparison with control was found. The lactic acid content was lower than 10g of the original matter in all samples of both variants. There were no significant differences in acetic acid content. The ratio of lactic to acetic acid was favorable in both variants (control- 4.9:1 and additive- 5.7:1). Undesirable butyric acid was not found in any samples. Addition of urea non-significantly (P>0.05) increased value of pH in grape pomace silages. The alcohol content was significantly (P<0.05) higher in silages without an additive.