The occurrence of eight carcinogenic N-nitrosamines in biosolids from 74 wastewater treatment plants (WWTPs) in the contiguous United States was investigated. Using liquid chromatography-tandem mass spectrometry, seven nitrosamines [( N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine, N-nitrosodi- n-propylamine (NDPA), N-nitrosodibutylamine, N-nitrosopyrrolidine, N-nitrosopiperidine (NPIP), and N-nitrosodiphenylamine (NDPhA)] were detected with varying detection frequency (DF) in 88% of the biosolids samples ( n = 80), with five of the seven being reported here for the first time in biosolids. While rarely detected (DF 3%), NDMA was the most abundant compound at an average concentration of 504 ± 417 ng/g dry weight of biosolids. The most frequently detected nitrosamine was NDPhA (0.7—147 ng/g) with a DF of 79%, followed by NDPA (7–505 ng/g) and NPIP (51–1185 ng/g) at 21% and 11%, respectively. The DF of nitrosamines in biosolids was positively correlated with their respective n-octanol–water partition coefficients ( R 2 = 0.65). The DF and sum of mean concentrations of nitrosamines in biosolids increased with the treatment capacity of WWTPs. Given their frequent occurrence in nationally representative samples and the amount of U.S. biosolids being applied on land as soil amendment, this study warrants more research into the occurrence and fate of nitrosamines in biosolids-amended soils in the context of crop and drinking water safety.