Whilst there is an increasing recognition of the circular economy concept within the building sector, opportunities for its implementation at project level remain largely underexploited. Research has shown that challenges to its uptake include limited knowledge and awareness among stakeholders; a fragmented supply chain; an unclear business model and financial case; and a lack of incentives to implement circular economy in building projects. Whilst these challenges are present across the construction supply chain, clients have a pivotal role in addressing them and driving the shift towards circular economy from project inception to completion. As such, clients can progress a number of enabling factors for the uptake of circular economy, including the implementation of innovative business models, whole life thinking, information sharing, facilitating supply chain collaboration and establishing a clear vision. This paper focuses on the role of the client in enabling a circular economy within the building sector by analyzing data obtained from a supply chain workshop on the critical success factors for implementing the circular economy. Supporting actions of the construction supply chain are also discussed. The results indicate that whilst a client can be influential in applying circular economy principles with a resulting reduction in material usage and waste generation through setting suitable conditions within the procurement process such as requirements for material efficiency, support from the construction supply chain is required to enable this to happen.