The effect of harvest interval (HI), six-, nine-, and 12-wk, and season of growth (winter, spring, summer, and fall) on crude protein (CP) and neutral detergent fiber (NDF) was studied with rhizoma perennial peanut (RPP) TARS line nos. 17033, 17050, 17052, and 17097 (PI nos. 276233, 262826, 262833, and 262839, respectively) and cv Florigraze and Arbrook at the Lajas Agricultural Experiment Substation. The same parameters were evaluated with PI nos. 276233, 262839, and cv Florigraze at the Juana Díaz Substation. The overall mean CP concentration for RPP, across HI and season of growth was 16.3 and 15.5% in the Lajas and Juana Díaz studies, respectively. In both trials, accession 17033 had the lowest (14.2%) and accession 17097 the highest (16.7%) CP values (P < 0.05). Harvest interval negatively influenced CP concentration (P < 0.01). An increase in HI from six to 12 weeks resulted in a reduction of CP from 17.3 to 15.5%, and from 16.5 to 13.7% in the Lajas and Juana Díaz studies, respectively. In the latter study the CP concentrations of forage harvested at six and nine weeks were similar. Differences in NDF among RPPs were significant (P < 0.05) in both trials. In both, accession 17033 had the highest (49.9%) and accession 17097 the lowest (48.1%) concentration. Increasing HI resulted in quadratic increases (P < 0.01) in NDF concentration. Results for the six-, nine- and 12-wk intervals were 47.8, 50.9, and 51.8% at Lajas and 45.8, 44.5, 52.0% at Juana Díaz, respectively. Season of growth did influence chemical composition of RPP; however, unlike the pattern observed in tropical grasses, the chemical composition of RPP was better in the seasons of greater forage yield (spring and summer). These results show the excellent potential for high nutritive value of RPP when grown in the Caribbean tropics.