<p>This study developed a simple, low-cost and industrially scalable method for collagen extraction from the skin of both cold and warm-water fishes while retaining the native triple-helical structure. Three fish species representing different skin compositions and different habitat temperatures: Tarakihi and Ling from New Zealand and Yellowfin tuna from Sri Lanka were selected to demonstrate its wide application to different raw materials. The method included extraction using hydrochloric acid to break cross-links while preserving the native triple-helical structure, homogenisation to speed-up the extraction and fibrillogenesis using sodium hydroxide to rapidly raise the pH to the isoelectric point. The effectiveness of this method was assessed by comparing collagen characteristics with a commercial biomedical-grade bovine collagen. The processing temperatures were well below the habitat temperatures, and fibrillogenesis at pH 9.3 resulted in higher yields of collagen with the retention of the native triple-helical structure as evidenced by FTIR absorption ratio, <i>R</i>_pn ratio from circular dichroism analysis and thermal properties by DSC. Higher denaturation temperatures of about 43&#xa0;°C were recorded for collagen extracted from the skin of both cold and warm-water species when processed well below their habitat temperatures. This study showed the ability to process collagen from warm-water fish species at 19&#xa0;°C, which saves energy at industrial-scale processing. This method employs a relatively few number of processing steps that omit complex centrifugation and dialysis techniques. This can be applied to any fish species of interest by adjusting processing conditions based on skin composition and habitat temperature. These developments represent promising factors for further commercial developments.</p>