Firefighters were called to Sheffield Cathedral on Thursday, finding smoke coming from a connecting charity building that provides food and facilties to people who are homeless.
It is thought the fire was started deliberately and South Yorkshire Police are currently treating the incident as a suspected arson attack.
Upon arrival, firefighters immediately gained access and extinguished the fire by 6.41pm, preventing any further spread.
The crew remained on scene for some time after the fire was out, clearing smoke from the building. There are no reports of any injuries and firefighters left the scene at around 10pm.
The fire was started in a room owned by the Cathedral and used by the Cathedral Archer Project, a homeless project that provides food, showers, internet access and health support to people trying to survive on the streets.
Access to the building is thought to be through a break in. A video of the building the following morning shows the incredible damage done.
In a statement, the charity said: "The intention is for CAP (the Cathedral Archer Project) to resume our essential services supporting and feeding homeless people, as soon as is safe and possible to do so. This is obviously a huge blow for the charity who have been making and delivering over 180 meals daily to those in need during this current crisis.
"We are so grateful for the messages of support, best wishes and donations that have come through so far. It is hugely appreciated."
Lots of clothes were damaged but the impact has been described as "localised inside," meaning after "a big clean up job" the charity could be up and running again as early as next week.
A 40-year-old woman from Sheffield was arrested nearby on Thursday evening on suspicion of arson and burglary and she remained in custody Friday morning, police said.
A Cathedral spokesperson said: "We have been overwhelmed by the outpouring of warmth, well-wishes and support following last night's fire at Sheffield Cathedral.
"The Cathedral has been a place for all people, a site of worship and community in Sheffield for nearly 1,000 years. Your offers of practical help and donations show that our mission and rich history remains at the heart of our city.
"We are still assessing the extent of the damage to the interior of the Cathedral. The fire was contained to the Domino Hall, but smoke damage extends to the rest of the building as well. When we know what's needed we'll ask for your support.
"The Cathedral Archer Project provide vital services to the most vulnerable in our society. Join us in supporting them so they can get back on their feet as quickly as possible."