Sea cucumbers belonging to the Holothuroidea class are a group of worm-like and soft-bodied echinoderms that live in nearly all marine environments. Mediterranean Holothuria tubulosa is an economic sea cucumber species found in Turkish seas. This study aimed to present the first report of detailed amino acid profile and investigate the biochemical and nutritional characteristics of H. tubulosa seasonally collected from one of the densest natural beds, located at canakkale Strait (Southern Coast of Marmara Sea), Turkey. According to our results, the highest protein, lipid, and ash contents (%) were found to be 10.2, 1.9, and 5.1, respectively. The highest percentages of saturated, monounsaturated, and polyunsaturated fatty acids were 42.9, 28.3, and 37.8, respectively. Total amino acids (mg/g crude protein) ranged between 867.2 and 974.0 among all seasons. All essential amino acids were found in body wall tissues and ranged between 7.1 and 5.9. Mineral composition was found to be desirable at the recommended and threshold levels. In general, the proximate composition of H. tubulosa was directly affected by seasons (p < .05); however, amino acid, fatty acid, and mineral compositions were found to be similar among all seasons, except summer (p > .05).