Urea was evaluated as a preservative for high-moisture alfalfa hay through trials designed to represent a forage producer’s use of the treatment. A device was developed to meter and distribute granular or powdered urea into hay at baling. When compared to untreated high-moisture hay, urea treatment provided a small reduction in heating during storage with a slight improvement in hay appearance and a reduction in spore numbers on hay following storage. When compared to untreated dry hay, urea treated high-moisture hay had much greater heating and loss during storage with greater fiber and fiber-bound protein contents following storage. The only consistent improvement provided by urea was an increase in crude protein content due to the nitrogen added through urea. The small benefit obtained would not justify the use of urea as a preservative of alfalfa hay.