Allen had announced earlier this month that the disease, which he had been treated for in 2009, had returned.
Allen's sister, Jody Allen, wrote in a statement: "My brother was a remarkable individual on every level. While most knew Paul Allen as a technologist and philanthropist, for us he was a much loved brother and uncle, and an exceptional friend."
Allen, who co-founded Microsoft with his childhood friend Bill Gates, had owned the Seahawks since 1997 and the Blazers since 1988. He's also the co-owner of the MLS' Seattle Sounders FC.
"Paul Allen was the driving force behind keeping the NFL in the Pacific Northwest," commissioner Roger Goodell said in a statement.
"His vision led to the construction of CenturyLink Field and the building of a team that played in three Super Bowls, winning the championship in Super Bowl XLVIII. The raising of the "12th Man" flag at the start of every Seahawks home game was Paul's tribute to the extraordinary fan base in the Seattle community. His passion for the game, combined with his quiet determination, led to a model organization on and off the field. He worked tirelessly alongside our medical advisers to identify new ways to make the game safer and protect our players from unnecessary risk. I personally valued Paul's advice on subjects ranging from collective bargaining to bringing technology to our game. Our league is better for Paul Allen having been a part of it and the entire NFL sends its deepest condolences to Paul's family and to the Seahawks organization."
Seahawks coach Pete Carroll was among several current and former Seahawks who tweeted their condolences and shared fond memories of Allen on Monday, as did Oakland Raiders running back Marshawn Lynch, who helped lead Seattle to its lone Super Bowl victory in 2014.
"Paul Allen was the ultimate trail blazer - in business, philanthropy and in sports," NBA commissioner Adam Silver said in a statement. "As one of the longest-tenured owners in the NBA, Paul brought a sense of discovery and vision to every league matter large and small. He was generous with his time on committee work, and his expertise helped lay the foundation for the league's growth internationally and our embrace of new technologies. He was a valued voice who challenged assumptions and conventional wisdom and one we will deeply miss as we start a new season without him. Our condolences go to his family, friends and the entire Trail Blazers organization."
Allen and Gates founded Microsoft Corp. in 1975. Microsoft's big break came in 1980, when IBM Corp. decided to move into personal computers. IBM asked Microsoft to provide the operating system.
The decision thrust Microsoft onto the throne of technology and the two Seattle-natives became billionaires. Both later dedicated themselves to philanthropy.
Over the course several decades, Allen gave more than $2 billion to a wide range of interests, including ocean health, homelessness and advancing scientific research.
Allen's influence is firmly imprinted on the cultural landscape of Seattle and the Pacific Northwest, from the bright metallic Museum of Pop Culture designed by architect Frank Gehry to the computer science center at the University of Washington that bears his name.
In 1988 at the age of 35, he bought the Trail Blazers. He told The Associated Press that "for a true fan of the game, this is a dream come true.''
Information from The Associated Press was used in this report.