Under a newly signed deal, the company becomes the exclusive partner of the Chicago-based Jones Lundin Beals and R3, which has offices in Singapore and Shanghai.
The arrangement extends Agency Insight's relationship with Jones Lundin Beals under which the pair worked to find specialist agencies for Vodafone and BP.
Andrew Melsom, the Agency Insight senior partner, said: "Any client looking at making global appointments or seeking benchmark information from around the world will be able to access our network at any location."
All three companies will retain their own branding while offering a seamless service across their territories. They are about to co-operate on an international training assignment for one client.
Greg Paull, the R3 managing director, commented: "More and more clients are looking for a world perspective, not just local."
Agency Insight has built a reputation as a client-led operation. It specialises in advising clients on how to get the best out of their agencies and will not necessarily recommend a review.