Police officers cordoned off Cambridge Street at Cowcaddens at around 8.10pm on Monday, following reports of a number of people taking unwell.
A 52-year-old man was pronounced dead at the scene, while a 37-year-old man was taken to hospital, where his condition is described as stable.
A 32-year-old woman and a 52-year-old man were treated by ambulance staff.
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Officers remained on the scene until Tuesday morning, and the street has now re-opened.
It is understood the incident is being treated as drug-related.
Enquiries into the incident are ongoing, but police said there are not believed to be any suspicious circumstances.
A Police Scotland spokesperson said: “Around 8.10pm on Monday, September 8, 2025, officers were called to a report of a group of people having taken unwell on Cambridge Street, Glasgow.
“Emergency services attended, and a 52-year-old man was pronounced dead at the scene. His next of kin is aware.
“A 37-year-old man was taken to hospital where he remains in a stable condition.
“A 38-year-old woman and a 52-year-old man were treated by ambulance staff at the scene.
“Enquiries are ongoing to establish the full circumstances but there are not believed to be any suspicious circumstances.”