To explore the potential use of Ecklonia cava as a natural dye for textiles, silk fabric was dyed with Ecklonia cava extracted by hot water under varied conditions, including temperature, duration, dye concentration, mordanting, and pH adjustment. The fabric was also evaluated for fastness, sun-protective property, and deodorization. Ecklonia cava extract was estimated by FT-IR to have polyphenol as a main functional colorant in plants, while the existence of phlorotannins through the UV-spectrum method was also confirmed. The fabric was optimized for maximum dye uptake at a temperature of 80°C for a duration of 50 minutes along all dye concentrations. The dyed fabric showed a hue of Yellow Red under all dyeing conditions while additional color tones, such as grayish and dark, were generated through mordanting and pH adjustment. Both good sunprotective properties and a positive deodorization rate were also recorded, with more than 20% (owf) Ecklonia cava extract on silk fabric. These results imply that Ecklonia cava has great potential to be used as an ecofriendly natural dye and in fashion goods with skin-health functions made of silk.