Crews from Brierley Hill and Haden Cross fire stations were called to the fire at the former Crown pub, on Simms Lane, Netherton, at around 3.17am today.
On arrival, they found a small fire on the ground floor of the two-storey, derelict pub, which was dealt with by firefighters wearing breathing apparatus and using hose reels.
Once the fire was put out, at around 3.38am, the crews used ventilation equipment to empty the building of smoke and fumes.
Officers from West Midlands Police also attended the scene and investigations with the fire crews found rubbish on the ground floor, which they believed to have been set on fire deliberately.
A spokesman for West Midlands Fire Service said: "We received a call at 3.17am about a fire at the Crown on Simms Lane in Netherton.
"Two fire engines from Brierley Hill and Haden Cross, with 15 firefighters in total, arrived at the scene five minutes later and said they saw a small fire on the ground floor of the disused two-storey pub.
"They believed the fire had been started deliberately, so wore breathing apparatus and used hose reels to extinguish the fire, with it confirmed out at 3.38am.
"They also used ventilation equipment to empty the building of smoke and fumes.
"West Midlands Police also attended the scene and we left the site in the hands of site security."
A West Midlands Police spokesperson said: "We were called following a fire at a derelict pub building in Simms Lane, Netherton, just before 4am today.
"It's being treated as arson and anyone with information can contact us via Live Chat or by calling 101. Quote 20DY/33660G/21."
Alternatively, contact Crimestoppers anonymously on 0800 555111 or at crimestoppers-uk.org