Walsh, a former tea party congressman from Illinois who is now a conservative talk radio host, tweeted, "On November 8th, I'm voting for Trump. On November 9th, if Trump loses, I'm grabbing my musket. You in?"
Walsh did not immediately respond to a CNN request for comment. But he did respond to CNN's Jake Tapper via Twitter when he asked: "What exactly does that mean?"
"It means protesting. Participating in acts of civil disobedience. Doing what it takes to get our country back," he responded to Tapper.
Dan Gross, president of the Brady Campaign to Prevent Gun Violence, condemned Walsh's tweet.
"Joe Walsh's continued vile and violent rhetoric has no place in our political discussion," he said in a statement.
Walsh has made apparent threats on Twitter before. In the wake of the Dallas police officer shootings over the summer, he tweeted, "3 Dallas Cops killed, 7 wounded. This is now war. Watch out Obama. Watch out black lives matter punks. Real America is coming after you."
At the time, he told CNN's Don Lemon that he stood by his words and that Twitter "shut me down."
"Twitter said the only way you'll open your account is if we get rid of that tweet," Walsh claimed in July.
At the time, Twitter would not comment on Walsh's claims, citing privacy and security reasons. But spokesman Nu Wexler noted a Twitter policy that says users "may not make threats of violence or promote violence, including threatening or promoting terrorism."