More than 150 plants were found growing under lights in a house in Leslie Road, Park Village early on Saturday morning.
Two crews from Fallings Park and Wolverhampton were sent to deal with an electricity box on fire in Leslie Road at 3.57am.
A fire engine and back-up vehicle with 10 firefighters attended the scene, where they found the box had burnt itself out.
However they soon found the cannabis farm in an adjacent property and tweeted saying "hmmm wonder what the cause was".
A West Midlands Police spokesman confirmed no-one was present at the address and enquiries are still continuing.
A second call-out took a crew from Wolverhampton to a car fire on Moseley Road at 4.45am.
A photo posted from the scene showed an Audi A5 left gutted by the suspected arson attack.
No-one was present at the scene and only one crew was needed to deal with the fire.
West Midlands Police officers were sent to both incidents.
A spokesman for the force said: "Fire crew alerted us at 5.10am to a car fire in Moseley Road, Bushbury. An Audi A5 was completely gutted in a suspected arson attack.
"Any witnesses are urged to message us on Live Chat via the website at WMP Online quoting log number 482 from 15 Feb."