Various N fertilizer sources are available for lawn turf. Few field studies, however, have determined the losses of nitrate (NO3–N) from lawns receiving different formulations of N fertilizers. The objectives of this study were to determine the differences in NO3–N leaching losses among various N fertilizer sources and to ascertain when losses were most likely to occur. The field experiment was set out in a completely random design on a turf typical of the lawns in southern New England. Treatments consisted of four fertilizer sources with fast- and slow-release N formulations: (i) ammonium nitrate (AN), (ii) polymer-coated sulfur-coated urea (PCSCU), (iii) organic product, and (iv) a nonfertilized control. The experiment was conducted across three years and fertilized to supply a total of 147 kg N ha−1 yr−1 Percolate was collected with zero-tension lysimeters. Flow-weighted NO3–N concentrations were 4.6, 0.57, 0.31, and 0.18 mg L−1 for AN, PCSCU, organic, and the control, respectively. After correcting for control losses, average annual NO3–N leaching losses as a percentage of N applied were 16.8% for AN, 1.7% for PCSCU, and 0.6% for organic. Results indicate that NO3–N leaching losses from lawn turf in southern New England occur primarily during the late fall through the early spring. To reduce the threat of NO3–N leaching losses, lawn turf fertilizers should be formulated with a larger percentage of slow-release N than soluble N.