Limited information is available for agricultural practices and operations in seed production of Italian ryegrass (Lolium multiflorum Lam.). The main objective was to determine the effect of plant growth regulator and nitrogen fertilization on the most important agronomic traits of Italian ryegrass grown for seed production. Field trial was carried out during one growing season with four nitrogen fertilization (0, 60, 120 and 180 kg/ha) along with unfertilized plots. Plant growth regulator Moddus 250 EC was applied during shooting at the rate of 1.0 L/ha. Seed yields averaged 1.652 kg/ha with average seed water content of 40.5%. Compared to untreated plots, the application of plant growth regulator reduced stem height, and consequently, increased seed yields. Nitrogen fertilization produced significantly higher seed yields primarily due to increased spike number and secondarily because of significantly higher 1000-seed weight and slightly improved floret number per spikelet. Seed yields following nitrogen fertilization rate of 120 and 180 kg/ha were slightly larger than those produced with 60 kg/ha. Nitrogen fertilization and plant growth regulator had no effect on final germination rate, but seed viability was higher for heavier seeds.