Saturday’s race was won by Daniel Abraham of Holland, with Brazil’s Lauro Chaman second and Andrea Tarlao of Italy third.
The road races began at Pontal and included the Grumari circuit incorporated in the Rio Olympics road races.
The Vista Chinesa circuit - which included a treacherous descent where Holland’s Annemiek van Vleuten crashed into the curb, sustaining heavy concussion - was not part of the Paralympic course.
Golbarnezhad was 14th in the time-trial on Wednesday and also competed at the London 2012 Paralympics. He was Iran’s sole cyclist at the Rio Games.
IPC president Sir Philip Craven said: “This is truly heart-breaking news and the thoughts and condolences of the whole Paralympic movement are with Bahman’s family, friends, and team-mates as well as the whole of the National Paralympic Committee of Iran.
“The Paralympic family is united in grief at this horrendous tragedy which casts a shadow over what have been great Paralympic Games here in Rio.”
Rio 2016 organising committee president Carlos Nuzman said: “This is very sad news for sport and for the Paralympic movement.
“Our hearts and prayers are with Bahman’s family, his team-mates and all the people of Iran.”
Brian Cookson, president of cycling’s governing body, the UCI, added: “I am devastated to hear about the death of Iranian rider Bahman Golbarnezhad.
“Our thoughts are with his family and friends, and the NPC of Iran to whom we offer our most sincere condolences.”
Realiran offers condolences to the family of the Golbarnezhad and Iranian sport community.