The N21 between Abbeyfeale and Castleisland has reopened following an earlier crash.
A man in his 80s is in a critical condition following the two-car crash happened shortly after 10am at Knockbrack, Knocknagoshel.
Four other people travelling in the second car were also taken to hospital for assessment.
The road was closed untul 6pm to facilitate an examination by Garda Forensic Collision Investigators.
Gardaí are appealing to anyone who witnessed the collision to come forward.
Road users with camera footage, including dash cam, who were travelling in the area at the time are asked to make it available to investigating gardaí.
Anyone with information is asked to contact Listowel Garda Station on 068 50820, the Garda Confidential Line on 1800 666 111, or any Garda station.
