This paper assesses the dissipation of napropamide and its impact on the activity of dehydrogenases, alkaline phosphatase, acid phosphatase, and urease in sandy clay loam. The experiment was carried out on soil samples with organic carbon content of 12.08 g·kg-1, total nitrogen content of 0.97 g·kg-1, and pH 5.24 with the following variable factors: (a) dose of Devrinol 450 SC formation (containing 450 g of naprop-amide in dm3): 0 (control), 0.5, 1, 2, 4, 8, and 16-fold hold of field dose; (b) day of experiment: 1, 7, 14, 28, 56, and 112. The half-life of napropamide ranged from 33.50 to 71.42 days. The use of napropamide at the dose recommended by the manufacturer and at the dose reduced by half appeared to exhibit low toxicity in relation to enzymes determined. In contrast, the application of elevated napropamide doses decreased the values of biochemical parameters of the soil in most cases. The Pearson’s correlation coefficients showed statistically significant negative correlation between the content of napropamide residues and the enzymatic activity of the soil.