Body temperature maintenance is one of the most important physiological processes initiated after birth. Brown adipose tissue (BAT) is an essential mediator of thermogenesis in many species and is responsible for 50% of the heat generated in the newborn lamb. To determine if maternal arginine supplementation could enhance thermogenesis in the neonate we randomly assigned thirty-one multiparous Suffolk ewes, gestating singletons or twins, to receive intravenous injections of either L-arginine (27 mg/kg bodyweight; n=17) or sterile saline (n=14) three times daily from Day 75 to Day 125 of gestation (term=147). Following parturition, lambs were removed from their mothers and subjected to 0°C cold challenges at 4 and 22 hours of age. Rectal temperatures were higher for the duration of the cold challenges in lambs from arginine-treated ewes compared to lambs from saline-treated ewes (P<0.05). Elevated rectal temperatures were associated with increased (P<0.05) circulating glycine and serine concentrations in lambs. The mRNA expression of genes related to BAT function changed over time, but not between lambs from arginine-treated versus saline-treated ewes. Results indicate that maternal arginine treatment increases neonatal thermogenesis after birth. Although the underlying mechanisms remain to be elucidated, these data are a first step in improving neonatal survival in response to cold.© The Author(s) 2020. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: firstname.lastname@example.org.