A person with knowledge of the negotiations confirmed the agreement, which cannot be formally announced until new contracts are finalized next Thursday. The deal, worth a reported $9.8 million, was first reported Thursday night by Yahoo! Sports.
Kaman confirmed the deal with a post on his official Twitter account.
''Portland is a great fit for me, it's a team that has done great things and has a lot of talent! Can't wait to get started in (hash)RipCity,'' he posted.
The burley 7-foot center has averaged 11.7 points, 7.9 rebounds and 1.4 blocks over an 11-year NBA career. He is expected to back up Robin Lopez with the Blazers.
He spent last season with the Los Angeles Lakers, averaging 10.4 points and 5.9 rebounds, but was limited to a career-low 18.7 minutes in 39 games. He struggled late in the season with injuries.
Kaman was the sixth overall pick in the 2003 draft by the Los Angeles Clippers. The Michigan native, who played at Central Michigan, was an All-Star with the Clippers in 2010, averaging a career-high 18.5 points and 9.3 rebounds, before he was traded to New Orleans the next season.
He played for the Dallas Mavericks in 2012-13 before signing a one-year deal with the Lakers. The Blazers will be his fifth team.
Portland went 54-28 last season, advancing to the Western Conference semifinals before losing to eventual NBA champion San Antonio.