The pair ran Coll & Cortés in Spain and merged with London’s Colnaghi in 2015.
From the new year Cortés will take on the gallery in Madrid, where he is based, which will become Nicolas Cortés Gallery.
Coll will continue with Colnaghi and the galleries in London and New York.
Although the companies will split, the pair are to continue to work together in partnership.
Cortés said: “Jorge and I have been discussing for some time how we structure the company which is now very international.
“I’m largely based in Madrid, where I also have my family and a number of other business interests. The structure will be different but we’ll still be working together.”
Coll added: “We’re like family, and we don’t want to stop working together having done so all our professional lives, so we decided to restructure the firm this way. There won’t be much noticeable change in day-to-day business and we’re already working on putting together an exciting exhibition for TEFAF in March 2019.”
Former Colnaghi chairman Konrad Bernheimer, who acquired the 258-year-old firm in 2002 and merged it with Coll & Cortés, retired during the summer.