The Rhode Island Democrat -- at times shouting himself hoarse in support of a measure pushed by Rep. Dennis Kucinich, D-Ohio, that would end the war -- derided the notion that Afghanistan "is a real country."
Instead, he labeled it a "loose collection of 121 different sovereign tribes, none of [whom] get along with each other."
But Kennedy blew his stack in response to a Republican lawmaker who said that ending the war would send a message of surrender to the family of a soldier killed in Afghanistan last year.
"Someone -- I can't believe I even heard this -- said, 'Oh, I can't go to a funeral and tell the parents of someone who just died that they lost their child in vain,'" Kennedy shouted with his eyes closed.
"Somewhere I heard that during the Vietnam War," he yelled. "So what is it we got to do? We got to double down on a bad policy to protect the honor of those who have already died? I don't think so."
"There isn't a solider in this country who's laid down their lives for our nation that isn't a hero. And no one in here disagrees with that. What is shameful is our policy that puts them in harm's way when they don't need to be."
Kennedy is the son of the late Sen. Ted Kennedy and the nephew of President John F. Kennedy. During his career, Kennedy has suffered repeated bouts with substance abuse. He took an extended leave from Congress last spring, spending time at a rehabilitation facility.
Kennedy's emotional speech Wednesday isn't the first time he's ignited fireworks on the House floor.
In his first term, Kennedy waged a legendary verbal scrap on the House floor with Rep. Gerald Solomon, R-N.Y., as lawmakers debated a repeal of the assault weapons ban..
On Wednesday, Kennedy also took aim at the media. Swinging his arm at the press gallery, Kennedy chastised the news media as "despicable" for not covering the day's debate as heavily as they did the recent troubles of Rep. Eric Massa, D-N.Y., who resigned Monday amid allegations he sexually harassed a male aide.
"There's two press people in this gallery," he shouted. "We're talking about Eric Massa 24-7 on the TV? We're talking war and peace, $3 billion, a thousand lives -- and no press? No press?
"You want to know why the American public is fit? They're fit because they're not seeing their Congress do the work that they're sent to do. It's because the press -- the press of the United States is not covering the most significant issue of national important and that's the laying of lives down in the nation for the service of our country. It's despicable, the national press corps right now."
Fox News' James Rosen contributed to this report.