Black pine (Pinus nigra Arn.) is found in Central and Southern Europe, Southwest Asia, the Balkan Peninsula, including Bulgaria's territory. The present paper aimed to investigate the phytochemical composition of unripe black pine seeds obtained from Bulgaria. Lipid fraction, was evaluated in unripe seeds, and cellulose, total carbohydrates, glucose, fructose, and sucrose were evaluated in seedcakes. The major fatty acid identified in the P. nigra seed oil was the unsaturated linoleic acid (44.2%), followed by the saturated palmitic acid (31.2%). The amount of unsaturated pinolenic (10.5%) and oleic acids (8.8%) was also rather high. The amino acid composition of the protein fraction of seedcakes was also determined. The amino acid composition was represented mainly by arginine (8.74 mg/g), phenylalanine (7.84 mg/g), lysine (7.50%), tryptophan (6.42 mg/g), valine (6.13 mg/g), isoleucine (6.00 mg/g), leucine (1.18 mg/g), and methionine (1.13 mg/g). The mineral content (N, P, K, Mg, Na, and Cu) of seedcakes was evaluated, as the amount of K (8048.00 mg/kg) and Mg (172.99 mg/kg) were the highest in the samples. These findings emphasized the potential use of the unripe black pine seeds as an alternative source of bioactive components in different areas due to their phytochemical importance and values.