Tuna skin, a byproduct of the fish processing industry, is used as an alternative collagen source to replace bovine and porcine products. This study aimed to extract collagen from tuna skin with acetic acid, and investigated the antioxidant activity. Collagen extraction was carried out through a pretreatment process, defatted with butyl alcohol, and soaking in acetic acid to extract the Acid Soluble Collagen (ASC). The effect of concentration of sodium hydroxide and soaking time on the non-collagenous protein removed were measured, and evaluated. The yield and antioxidant activity of each sample were evaluated and the best result was determined by ANOVA. The highest yield of collagen was 3.18% based on dry weight reached at the treatment with sodium hydroxide 0.2 M and acetic acid 1 M. The different treatments did not result in any significant differences in the spectrum of amide A, B, I, II and III which are the characteristics spectra of collagen. Based on the electrophoretic pattern, tuna skin collagen has , and one β chain. Therefore, it is classified as type I collagen. The main amino acids were glycine and proline. In addition, the strongest antioxidant activity was found in the sample treated with sodium hydroxide 0.05 M and acetic acid 1 M treatment with IC50 value of 0.45 mg/mL. This study is the first to report on antioxidant activity from fish collagen (not hydrolysate or peptide products).