Dan was born and raised in Boston, and graduated from Suffolk Law School in Boston. After graduating, Dan spent nearly 10 years working in Boston as a bankruptcy lawyer, but the work made him weary.- he felt stagnant and unfulfilled,.Harrington now runs Anchor Loans, where he loans money while at the same time investing in the stock market and real estate.
He excelled at all types of games as a child, and played chess, backgammon and poker while attending university. In fact he was a state chess champion in 1971 and won the World Cup of Backgammon in 1980. In Danís college years he played poker with some students from Harvard including Bill Gates and his Microsoft co-founder Paul Allen. As the popularity of bridge faded, poker took on a new luster, hold'em became the dominant game at the Mayfair Club in New York City. The core group of players there included Dan, Jay Heimowitz, Al Krux, Erik Seidel and Steve Zolotow.
By 1990, Al Krux had placed 6th in the World Series of Poker main event, and in 1988, Steve Zolotow took 5th in an Omaha tournament while Erik Seidel was finishing second to Johnny Chan in the main event. However, in 1987, the $10,000 tournament was simply dominated by the Mayfair Club regulars. Approaching the final table of the WSOP main event, Jay Heimowitz was knocked out in 11th place. Next came Dan, playing in his first championship event, who finished 6th and collected $44,000. A young Howard Lederer, playing in his first WSOP event finished 5th and collected $56,000.
At the WSOP in 1995, Dan obtained one of his goals - winning a gold bracelet. His win in the $2,500 No Limit Hold'em tournament game him a quarter-million dollars to play with, so he entered the $10,000 main event again. Just a few days after his first win, Harrington made the final table and stared at his stack of chips. He wasn't leading, and in typical Harrington fashion, assessed his chances of winning and then proposed a nine-way split between the remaining players. They passed. After three players were knocked out, Dan's stack stood at just over $532,000 and he held down second place to Howard Goldfarb's $1.2 million. Again, Harrington proposed a split. This time, he tried to explain that with $2.2 million remaining in prize money they could each walk with enough money to invest and live comfortably. He even offered to help them invest their winnings, but the other players passed on his offer - so he busted 'em all and took the $1 million dollar first-place check for himself. For most players, making the final table of the Main Event at the WSOP would be a once in a lifetime event, but Dan isn't like most players he returned to the WSOP in 2003 and made the final table again, taking down third place and winning $650,000 and in 2004, Dan repeated the feat, finishing fourth in a much larger field and won $1,500,000.
Dan is known as a very tight player, hence his ironic nickname, "Action Dan".
As of 2005, his live tournament winnings exceed $4,400,000.
Dan's winning WSOP hand:
Howard Goldfarb raisied preflop with A7 and Dan called. When the flop fell 826 Dan checked with his pair, but Howard then moved all in. Dan quickly called, as if he knew Howard had nothing. The turn and the river brought a pair of queens, and Dan's pair of 8's held up.