Amino acid supplementation in cervids is an almost unexplored research area. Lysine (Lys) and Methionine (Met) are the two amino acids considered as limiting for ruminants and Lys supplementation shows good potential for increased antler growth as it is the main component of collagen and a bone tissue precursor. However, several studies in other ruminants have shown greater effects when simultaneously supplementing Lys + Met. Two experiments based on Lys and Met supplementation during first antler growth were conducted during two consecutive years. Each experiment involved 45 yearling fallow bucks distributed in three groups, balanced by weight: Exp.1: Pasture, Pasture + Barley (0.2 kg/animal per day), and Pasture + Barley + Lys (5 g/animal per day); Exp.2: Pasture + Barley (0.5 kg/animal per day), Pasture + Barley + Lys (9 g/animal per day), and Pasture + Barley + Lys + Met (9 and 3 g/animal per day, respectively). Lys supplementation during the first experiment did not improve any antler characteristics (P > 0.05). However, in the second experiment, both Lys (9 g) and Lys + Met treatments had positive effects on the external antler characteristics (P = 0.013), antler weight (P = 0.061) and particularly on the burr perimeter (P = 0.008), which is crucial for antler size in following years. The results also suggest a stronger positive effect of amino acid supplementation on antler growth when the animals have a low performance in the presence of poorer pasturing situation.