Background: The retail sector is rapidly developing over the past years. Retailers are investing more efforts and resources to provide a seamless experience through multiple channels. These developments led to significant changes in customer behaviour. Customers buying activities and way of selecting the products and retailers faced different changes and developments. The online retailing sector is entitled to continuous development. The latest development was due to the Covid-19 global pandemic that came without any previous notice. The customer behaviour starts adopting the digital online channels in most of their needs and wants. The appearance of new customer behaviour patterns due to Covid-19 lead to the emergence of new customer behaviour.Purpose: This study is of an exploratory and constructive nature. It is concerned with deepening the knowledge about the change in customer buying behaviour brought by Covid-19 on the retailing sector. The aim of the study is to identify and test new behavioural patterns that would influence the Swedish millennials’ in selecting between online and offline stores for shopping and buying fashion products.Method: An abductive approach was followed in this paper. Mixed methods of both qualitative and quantitative were used to fulfil the purpose of this exploratory research. The research followed a sequential exploratory design of two data collection phases. Theiiempirical data was conducted from (4) focus groups sessions with a total number of (20) interviewee, and (94) relevant responses from a web-based survey.Conclusion: The study has revealed two significant findings and contributed to propose a conceptual model. The fruitful results of this study are: (1) there is a vast customers’ migration towards online stores. (2) there are new behavioural patterns related to Covid-19 that are influencing the customer buying behaviour. (3) A proposed conceptual model which is concerned with the factors influencing the customer buying behaviour in selecting between online and offline fashion stores.