The auctioneer previously worked with Cream UK, which decided not to repitch. It has appointed the independent agency AdConnection ahead of an anticipated increase in its UK marketing activity.
Bonhams is currently investing in an expansion programme that will include the construction of a new London auction house and expanding its business into new overseas markets.
David Johnson, the marketing director of Bonhams, said: "AdConnection impressed us with its senior team who can turn things around quickly and who have the creativity and results to maximise our campaigns."
Catherine Becker, the chief executive at AdConnection, said: "We are looking for the best partnerships with media owners to maximise value for their business."