We conducted monthly nutrient addition experiments (May-Nov 2007) in a perennial, spring-fed tributary of the Ivishak River, Alaska to determine NH₄-N and PO₄-P uptake dynamics.  Using multiple-concentration amendments of combined N+P and single-concentration amendments of N or P only, we found no measurable P uptake along the 200-m study reach. N uptake lengths (S_w) ranged from 36 to 237 m, with the shortest S_w values occurring during summer.  There were no significant differences between S_w values calculated from solo N additions and from combined N+P additions at the same concentration, suggesting that additions of P did not alter N uptake.  Neither was the magnitude of N added in our combined additions sufficient to overcome stoichiometric constraints preventing measurable P uptake by stream biota.  N uptake velocity was rapid (0.13 - 0.87 mm·s^-1), with peak values in late spring-early summer. Our combined data suggest that this spring-fed stream is strongly nitrogen-limited.  Apparent N-limitation is unusual for streams of Alaska’s North Slope, where previous studies have consistently indicated strong P-limitation.  If other arctic springs exhibit similar nutrient limitation conditions, they likely confer considerable heterogeneity in nutrient regime and aquatic ecosystem processes across this arctic landscape.