Police, ambulances and a North West Air Ambulance helicopter were called to Parliament Street at around 10am yesterday (Sunday).
The area between Branch Road and Plumbe Street was taped off to allow emergency services to attend the scene.
Police confirmed the man, who has not been named, was rushed to Royal Blackburn Hospital, but died a short time later.
A spokesman for Lancashire Police said: "We were called around 10am yesterday (Sunday, August 15th) by the Ambulance Service after a man had been found unresponsive in Parliament Street, Burnley.
"Emergency services attended with the man, aged in his 50s, taken to Royal Blackburn Hospital for treatment. Sadly, he died a short time later.
"The death is not being treated as suspicious and a file will be passed to the coroner.
"Our thoughts are with the man's family at this sad time."