Abstract. Yuniati R, Sulardiono B. 2019. Exploration of the collagen of non commercial sea cucumber Holothuria atra and commercial sea cucumber Stichopus vastus in the Karimunjawa Islands, Indonesia. Ocean Life 3: 18-23. The commercial value of sea cucumber needs to be explored because of the availability of bioactive compounds that play an important role in biological activities, including collagen. However, based on the content of compounds, each species has its own variety of values. This study aims to determine the partial characteristics of collagen content of sea cucumber Holothuria atra as a non-commercial sea cucumber and of sea cucumber Stichopus vastus as commercial sea cucumber in Karimunjawa, Central Java Province, Indonesia. The preparation stage includes the stages of sampling of sea cucumbers H. atra and S. vastus, followed by the cleaning and washing, and soaking in distilled water, in alcohol, in a solution of Tris-HCl and ethyleneadiaminatetraacetate (EDTA) and, at last, in sodium hydroxide (NaOH) solution. It was continued by the extraction with immersion of 0.5 M acetic acid solution, and the isolation by precipitation in NaCl and dialysis solutions. In conclusion, the yield extract of H. atra and S. vastus both had no different values, namely 0.88% and 0.92% and it was classified as low. The whiteness degree of H. atra collagen was 61.60 ± 0.57% and it was higher than the degree of sea cucumber S. vastus which was 20 ± 1.00%. The functional group of sea cucumber H. atra consists of an amide with wave number of 3460.96 cm-1 and alkene with a wave number of 1636.77 cm, while in the functional collagen group, sea cucumber S. vastus contains amide with wave absorption number of 3434.28 cm-1 and alkene with wave absorption number of 1639.46 cm-1 and the strong absorption peak at 1033.85 cm-1 indicating the presence of free (C = O) bonds. The data and information obtained is used for the biological resource management plan in Karimunjawa.