Dumpsters were set on fire on the 1900 block of West Cuyler Avenue and on the 4000 block of North Damen Avenue, said police.
According to an officer at the scene, one of the fires was threatening to spread to a nearby utility pole.
The arsonist was described as a white male in his 20s, about 6-feet-tall, wearing a black vest and a white hat.
The offender was last seen running eastbound on West Irving Park Road.
At 11:48 p.m., police stopped a possible suspect at Wolcott and Belle Plaine Avenues.
As of 11:58 p.m., it was unclear if the possible suspect was identified as the man who set the fires.