Marandu palisadegrass (Brachiaria brizantha cv. Marandu) is the most widely planted grass for forage production in Brazil. Although nitrogen (N) fertilization can increase forage productivity and quality, the high cost of commercial fertilizer has prompt the need to evaluate N sources that optimize forage responses. The objective of this experiment was to evaluate crude protein (CP) fractionation concentrations of Marandu palisadegrass in response to N sources (urea, urea treated with urease inhibitor, polymer coated urea, ammonium sulfate, ammonium nitrate, ammonium sulphonitrate and control treatments). The field experiment was conducted in Ilha Solteira, SP, Brazil (20^o 21^’ S, 51^o 22^’ W and 226 m) from Nov. 2012 to Jan. 2013.  The experimental design was a randomized complete block design with four replications. Nitrogen sources showed no effect on protein concentrations associated with Fractions A (rapidly degradable) and B (potentially degradable) in all harvests. Average concentrations of the Fraction A during the 3 harvests were (313.2, 378.3 and 348.9 g kg^-1 CP), respectively and Fractions B were (595.6, 522.2 and 540.5 g kg^-1 CP), respectively in first, second and third harvest. For Fraction C (undegradable in the rumen), concentrations in the second and third were not affected by N sources and average concentrations were 106.6 and 124.2 g kg^-1 CP, respectively. The first harvest concentrations of protein associated with Fraction C were affected by N sources in the first harvest, where the greatest concentrations were obtained with urea. Because protein concentrations associated with the various fractions did not differ with the N source, data indicate that urea may be the best option because it’s lower cost and higher N concentration.