Innovation steps in complex products often go hand in hand with the selection of suppliers. The suppliers are involved in the development of innovative elements of products, supplementing the capabilities of companies. Strategic relationships are established with these suppliers, where the companies need them to be flexible and willing to adapt to changing demands. Flexibility is usually evaluated against a variety of indicators. However, a high score on flexibility does not guarantee cooperative suppliers. Companies also require power to get a supplier to be flexible. They need suppliers who are malleable to their changing needs that are an inevitable part of design processes. The empirical study at a leading European engine company reported in this paper shows that the relative power between companies and suppliers influences the responsiveness of suppliers to requests. This paper analyses malleability as a combination of flexibility and relative power. It unpacks power and flexibility into sets of measurable indicators and proposes a tool which assesses both the relative power between buyer and supplier and the supplier's flexibility, to provide a malleability index, which indicates to what extent a supplier is suitable to work with. Index Terms-Decision making, malleability index, flexibility, power, product innovation and development, TOPSIS Managerial Relevance Statement-Companies require suppliers who are able and willing to respond to the changing needs of companies during the innovation processes. This is not only a matter of the flexibility of suppliers, but also of the relative power of companies to make suppliers flexible. The malleability index proposed in this paper offers managers a convenient way to assure that the selected suppliers are not only technically competent and cost effective, but also willing to be flexible in a way to suit the needs of the companies to enable innovation. This paper also contributes a decision tool for industry, which assesses the malleability of suppliers. It follows a simple logic to weight up different indicators and compare the indicators against a best and a worst case scenarios. The tool also helps different decision makers to reach a consensus about the weights of the indicator and the performance of the suppliers against each indicator, thereby it allows the decision makers to reflect over their priorities.