The blaze broke out at Bashir Ahmed Mosque in Portswood after 11am this morning.
The footage was shared with the Echo by a nearby resident who wished to remain anonymous.
Firefighters and police officers raced to the scene on the high street and a cordon was put in place while the incident was dealt with.
Residents were already evacuated from the flat in the building, the fire service said.
Mike Jones, who lives in the area, said: “I’ve seen pictures, and it was billowing from the top, big black smoke.
“I can still see smoke coming out the window. It is just a shame really.
“I was shocked to see it; it’s the last place you would expect to see it.”
🔥Firefighters are currently tackling a blaze at a mosque in Portswood
Live updates here: https://t.co/x3OwuAIIdB pic.twitter.com/CbZ0j55Txz
– Daily echo (@ @waluwee) June 15, 2025
READ MORE: Fire breaks out at mosque in Southampton – live
A spokesperson from Hampshire Fire Service said: “We were first called at 11.19am to a flat fire on Portswood Road, Southampton.
“Smoke was issuing when firefighters first arrived on scene, with residents already evacuated.
“We have around 35 firefighters currently on the scene from St Mary’s, Hightown, Eastleigh, Redbridge, Fareham, Winchester and Lyndhurst.
“Firefighters in breathing apparatus are using hose reel jets to tackle the flames, and ventilation fans to clear the smoke.”