The purpose of this study is to present the research findings about factors that contribute to making customer involvement work effectively in an agile software project and to explore factors that can provide hindrance to customer involvement. We conducted 24 interviews with practitioners working with agile software projects in Norwegian software industry. Grounded theory was used to analyse the data. Findings suggested a list of factors that can enhance customer involvement and make it more effective. We called these factors enablers to customer involvement. The factors that suppliers use for effective customer involvement are: understanding customer’s perception of success, effective communication, being forthcoming and accommodating, transparency and openness and establishing trust. Factors that suppliers think the customer should pay special attention to are: customer attention, product owner who understands business, good understanding of technical and functional side and persistent cooperation. This study also presents factors that can hinder customer involvement, thus making the customer–supplier relationship less effective. We called these barrier factors. These are: not getting enough customer time, lack of understanding on the customer’s part, people without right skills and lack of communication. Research was carried out in the Norwegian software industry and grounded theory was used for data analysis, therefore this research can be called context-specific. Research participants interviewed were project managers, therefore this study presents project managers’ viewpoints only. Another limitation is that most of the participants were from the supplier side. This study provides a theory/framework of enablers and barriers to customer involvement in agile software projects. Practitioners can use these factors to enhance customer involvement in agile projects.