Chalian's comment, which was picked up by a microphone and turned up in an Internet video, was a reference to the Republican National Convention festivities and the flooding caused by Hurricane Isaac.
"David Chalian's statement was inappropriate and does not represent the views of Yahoo!," the company said in a statement disclosing his dismissal hours after the video hit the Internet. "He has been terminated effective immediately. We have already reached out to the Romney campaign, and we apologize to Mitt Romney, his staff, their supporters and anyone who was offended."
Chalian posted an apology on Facebook that the Washington publication Politico reported was only viewable to "friends" of his account.
"I am profoundly sorry for making an inappropriate and thoughtless joke," Politico quoted his statement as saying.
"I was commenting on the challenge of staging a convention during a hurricane and about campaign optics. I have apologized to the Romney campaign, and I want to take this opportunity to publicly apologize to Gov. and Mrs. Romney.
"I also regret causing any distraction from the exceptional coverage of the Republican convention by Yahoo! News and ABC News."