This thesis was done in order to investigate how social media and the growth of e-commerce influences the purchase of fast fashion clothes and sustainability. The thesis explored how e-commerce affects consumer perceptions of fast fashion, how social media influences consumer choices, the relationship between sustainability awareness and shopping behavior as well as how e-commerce's accessibility affects the traditional brick-and-mortar retail stores. The results showed that a large number of environmentally concious consumers still proceed to buy fast fashion clothes, with an increase preferences in online shopping. Despite concerns about sustainability, consumers often prioritize and frequently took convenient options over sustainable ones. Additionally, Consumers' top sustainability concern was the usage of eco-friendly materials by online retailers, and they also anticipated that online shopping will become even more sustainable in future years. This study emphasises on how businesses must change to meet consumer expectations while establishing more environmentally friendly e-commerce practices.