The collision took place on Kennel Hill on Friday, June 10, between a black BMW M1 and a black Ford Mondeo.
Both drivers suffered serious injuries, police have said, and a 67-year-old man – the driver of the Mondeo – sadly died less than a week later on Thursday, June 16.
A spokesperson for Sussex Police said: “Police are appealing for information after a man sadly died in the days following a collision in Chichester.
"Officers responded to a report of a head-on collision between a black BMW M1 and a black Ford Mondeo on Kennel Hill around 4pm on Friday, June 10.
"The drivers of both vehicles suffered serious injuries, and two passengers suffered minor injuries.
“As part of the ongoing investigation, officers are requesting that anyone who witnessed the collision or who may have captured any relevant dashcam footage emails [email protected] quoting serial 889 of 10/06.”