ANC spokesperson Jackson Mthembu said a bottle containing chemicals was left under a couch in the reception area in order to start the fire, which occurred Tuesday.
Security forces were at headquarters in the Luthuli House when the blaze broke out and were able to put it out quickly, Eyewitness News, Johannesburg, reported.
Damage was minimal and no one was injured.
Mthembu said the ANC is more concerned about the intention behind the incident.
"In our view this was an attempt to burn down Luthuli House and indeed it's something we obviously condemn. We view this in serious light as it appears to be an act of attempting to destabilize the ANC through acts of arson and sabotage," he said.
Police are investigating the fire and examining security camera footage, Eyewitness News reported.