Studies of supplier involvement in product development have revealed potential benefits including faster time to market, reduced cost and increased quality. However, existing literature has mainly focused on the customer's perspective on advantages, disadvantages and factors to be considered when involving suppliers in product development. This paper addresses the supplier's perspective by answering following research question: How do challenges that originate from involvement in customer's product development affect a supplier? The question is answered through a single case study at a supplier that develops and manufacture products primary used in capital goods. Thirteen challenges are identified, classified as being internal or external, and categorised into five areas: (A) Customer requirements, (B) Information exchange between customer and supplier, (C) Product variety management, (D) Design- manufacturing integration and (E) Processes and work instructions. The findings suggest that internal challenges need as much attention as external ones that originate from the customer. Also, an indication of when the challenges affect the supplier during product development is presented.