Police wouldn't release the actor's name, but a statement from the Fox studio and network on which "Empire" airs identified him Tuesday as Jussie Smollett.
A statement from Chicago police says the man said he was walking downtown about 2 a.m. Tuesday when two men approached him shouting, then struck him in the face and poured an "unknown chemical substance" on him before one wrapped a rope around his neck.
Police say he was hospitalized in good condition.
"Given the severity of the allegations, we are taking this investigation very seriously and treating it as a possible hate crime," the police statement said.
Smollett has starred on Fox's "Empire" since 2015. He plays Jamal, a successful singer in the musical Lyon family. Like his character, Smollett identifies as gay.
"We are deeply saddened and outraged to learn that a member of our 'Empire' family, Jussie Smollett, was viciously attacked last night," a representative of 20th Century Fox Television and Fox Entertainment said in a statement. "We send our love to Jussie, who is resilient and strong, and we will work with law enforcement to bring these perpetrators to justice. The entire studio, network and production stands united in the face of any despicable act of violence and hate -- and especially against one of our own."