An increase in game meat consumption has been observed worldwide. This is the first study to assess the amino acid composition and the protein quality of the muscles of deer from organic feeding grounds. This study assessed the nutritional value of the protein of the muscles of deer originating from forest, organic, and conventional feeding grounds. The meat of deer from the forest and the conventional feeding grounds exhibited higher exogenous and endogenous amino acid contents than that of deer from the organic feeding ground. However, the meat of deer from the organic farm feeding ground is characterized by the highest protein content and ensures optimal satisfaction of the demand for essential amino acids. The highest lysine content was found in the muscles of the deer from the forest feeding ground. This knowledge can help nutritionists develop diets that meet the nutritional recommendations for different consumer groups and breeders to make decisions about farm location and deer feeding strategies.