The significance of garment and fabric dyeing methods on colourfastness, cost-effectiveness, and aesthetic outcomes of the clothing manufacturing process are the primary goals of this study's comparative analysis. The study looks at how each technique affects the final look and standard of clothing, concentrating especially on fashion and casual wear.Following ISO guidelines, fabric samples and finished clothing were dyed using each approach in a controlled environment and tested for colourfastness to light, rubbing, and washing. Cost analysis was performed out by looking at workforce, material, and processing costs at different stages of manufacturing. Objective visual inspections were also conducted to evaluate visual attractiveness, colour depth, and surface uniformity. According to the findings, garment dyeing gives greater design freedom, better garment uniqueness, and possible cost savings in small batch manufacturing, whereas fabric dyeing delivers higher quality colour uniformity and improved colourfastness. Particularly in the context of fast fashion and customized apparel, this study helps designers and manufacturers choose the best dyeing technique depending on product type, batch size, and end-user needs.