Informal markets for fashion are a growing phenomenon around the world and more specifically in the Democratic Republic of Congo. In different cities in the Democratic Republic of Congo, there are tents housing vendors who sell second-hand clothes. These markets are becoming the millennials' shopping hubs as millennials are on a quest for uniqueness, fashion trends and value for money. Limited research regarding the shopping patterns and purchase decisions of Congolese millennials and even less regarding the informal clothing market in the Democratic Republic of Congo is available. This research is aimed at investigating factors influencing millennials in the purchase of second-hand clothes in the informal markets in the Democratic Republic of Congo. The theoretical framework was guided by the theory of planned behaviour from which the researcher constructed an adapted model. The purchase of secondhand clothes is the behaviour that is preceded and influenced by the consumer's intention to purchase. In turn, the intention to buy clothing from informal markets is influenced by various factors. Five factors were added to the model, namely quality, clothing interest, peers' opinions, price consciousness and the need for uniqueness. The model was investigated through a qualitative case study analysis. The data was collected through face-to-face interviews and the thematic analysis was conducted and interpreted manually. The target population argued that second-hand clothes are unique, durable and affordable. These clothes allow them to shop the fashion trends they see on social media from around the world. Thus, it is important to have a valuable understanding of the factors influencing Congolese millennials to buy second-hand clothes. Retailers and marketers in the fashion industry of the Democratic Republic of Congo, particularly those in the informal clothing market, can consider the consumer insights acquired in this research and apply them to increase their advantage in the market place.