Harrington first cashed in the World Series of Poker in 1986. The next year, in only his second WSOP cash, Harrington made the final table of the Main Event; he finished in sixth place in the event, which was won by Johnny Chan. Harrington’s friend and fellow Mayfair Club member, Howard Lederer was also at this final table, finishing fifth.

Also, in 1995, he won a bracelet in the $2,500 No-Limit Hold’em event for $249,000 and the Seven-card stud event at European Poker Open in London. He made his first final table at the World Poker Tour (WPT) in 2005, winning $620,730 for his second-place finish to Minh Ly in the Doyle Brunson North American Championship.

His solid play allows him to make it to many final tables at large events. He won the World Series of Poker (WSOP) Main Event in 1995 for $1,000,000. He has made three other Main Event final tables: placing sixth in 1987 for $43,750, third (out of 839 players) in 2003 for $650,000, and fourth (out of 2,576 players) in 2004 for $1,500,000. Because of the increased number of participants, his run of back-to-back Main Event final tables in 2003-04 has been called the greatest accomplishment in World Series history, particularly by ESPN poker announcer Norman Chad. This feat was later matched by Mark Newhouse in 2013 and 2014. As defending champion in 1996, Harrington made another deep run in the Main Event, finishing in 17th place and earning $23,400. He also cashed in the 2009 Main Event, finishing in 252nd place for a $32,963 payout.

In addition to being a successful professional poker player, Harrington also works in real estate and the stock market. Mr. Harrington is a co-founder and former member of the Board of Directors of Anchor Loans, a hard money lender to fix-and-flip and rental property investors that is headquartered in Calabasas, CA. Harrington co-founded the company in 1998 with two poker buddies, Jeff Lipton and Stephen Pollack, and served as its first Chief executive officer. The trio used their poker winnings to provide quick bridge funding to real estate rehabbers. Anchor Loans has since funded more than 5.3 billion in loans and has been profitable every year since its inception. Harrington retired from Anchor Loans in 2010, but remains a shareholder. He has also stated during interviews about his poker career, that he is there for the money, not the fame or glory. Also unlike many professional poker players, Dan considers himself only a part-time player due to the fact that he spends a large amount of his time on his business interests. He usually only plays a few events at the World Series of Poker each year and plays in occasional World Poker Tour events and a few other tournaments.

In 2007, he won the Legends of Poker for a prize of $1,634,865.

In 2008, Harrington made his first appearance on the NBC show Poker After Dark in the episode titled “Mayfair Club.” This tournament brought together poker players who had played at the legendary Mayfair Club in New York City. The other players in the tournament with Harrington included professional poker players Lederer, Mickey Appleman, Steve Zolotow, Jay Heimowitz, and Mike Shictman, the owner of the Mayfair Club for many years. Harrington busted out first, finishing in sixth place. The tournament was won by Heimowitz, who defeated Lederer in heads-up play.

In 2010 Harrington was inducted in to the World Series of Poker Hall of Fame.

As of 2014, his live tournament winnings exceed $6,600,000, which he accumulated over a period of 34 years, cashing in 52 events. More than half of his live tournament winnings ($3,524,476) have come at the WSOP.