Studies have shown that calves fed milk replacers (MR) with crude protein (CP) concentrations greater than 20% typically found in conventional MR have higher dry matter intakes (DMI) and greater average daily gains (ADG), but consume less starter which can lead to stress during weaning and reduced rumen development. The greater amount of CP being fed to preweaned calves may alter their nitrogen (N) balance and excess N may be excreted in the urine. The objective of this study was to determine N utilization in preweaned calves fed diets varying in the amount of CP and MR fed. This study used 24 newborn dairy heifer calves blocked by birth and randomly assigned to 1 of 3 treatments: (1) 454 g of a conventional MR (C; 20% CP, 20% fat), (2) 680 g of a moderately high protein MR (MMR; 26% CP, 17% fat), or (3) 908 g of a MMR (HMR; 26% CP, 17% fat). All calves had free choice access to starter and water. Both MR and starter were medicated with decoquinate. During weaning (d 43–49), AM MR feeding ceased. On d 50, all MR feedings ended; however, starter and water intakes were continuously recorded until d 56. At 5 wk of age, urine was collected using urinary catheters for 3 d and chromium oxide was administered by bolus at 2 g/d for 7 d to estimate N efficiency. Calves fed MMR and HMR had similar starter intakes, feed efficiencies (FE), and ADG; with the combined treatments having reduced starter intakes (258 g/d vs. 537 g/d), greater ADG (674 g/d vs. 422 g/d), and improved FE (0.57 vs. 0.45) compared with the C calves preweaning (P < 0.05). However, DMI and water intake were similar across all treatments. Results from the N utilization phase showed that MMR and HMR treatments had similar but lower N efficiency than C calves (45.5% vs 52.7%; P < 0.05). This could be due to MMR and HMR fed calves having greater urine volume; and thereby, greater combined urine N output compared with C calves (17.6 g/d vs 12.1 g/d; P < 0.05). In summary, feeding a moderately high protein MR increased ADG and improved FE during the preweaning period, but reduced starter intake and lowered N efficiency.