The accident happened at Grove Road, Harold's Cross Bridge at about 10.30am.
Gardaí say the man, who is believed to have been in his 30s, was fatally injured when his bicycle was involved in a collision with a cement truck.
No one else was injured in the crash.
The road was closed pending technical examination and traffic diversions were in place.
Gardaí are appealing for information on the collision.
Anyone with information can contact gardaí at Terenure on 01 666 6400 or the garda confidential line 1800 666 111.
