In later life, Mahmoud Khayami has been active as a philanthropist and collector of fine Persian art, forming the Khayami Collection. He has promoted inter-religious relations in the UK and internationally with a special emphasis on relations between the Jewish, Christian, and Muslim communities. Among his activities have been the hosting at Chatham House (RIIA) of inter-religious conferences. He was involved with the
Encyclopædia Iranica project and chaired the board of editors.