The 54-year-old suffered serious head injuries after he was struck by a purple-coloured Peugeot 107.
The accident happened on Balmoral Street at around 1.10pm on Sunday at the junction with Dumbarton Road.
The pedestrian, who has not yet been named, is being treated at the Southern General Hospital. His condition has been described as "critical".
Police Scotland is appealing for witnesses.
Police constable John O'Hara of Police Scotland said: "I know the area was busy at the time and there are a number of drivers and pedestrians who may have witnessed the accident.
" I would like anyone who saw anything at all to contact me as every little detail helps us build a complete picture of what happened."
Anyone with any information should contact PC O'Hara at Police Scotland on 101.