An arson investigation was underway after the incident.
“The incendiary device did not ignite when it was thrown at the Travis County Democratic Party headquarters,” Austin Fire Captain Brandon Jennings said in a statement.
A small stack of papers was set on fire and was quickly put out with the help of a fire extinguisher by employees from a neighbouring business.
The county office was empty at the time, though the incident was caught on security cameras.
Travis County Democratic Party Chairwoman Katie Naranjo mentioned that a note with a politically motivated threat was left behind.
“Anyone who wears an American flag as a bandana and then throws a Molotov cocktail ... into a building and leaves a note, a threatening note, is a coward,” she said.
Authorities did not release the contents of the note.