Miller's contract is a three-year deal worth $21 million, with $14 million guaranteed and $7 million included as a third-year team option, sources close to the process said.
Miller, an unrestricted free agent, had been balking at signing a one-year offer from the Philadelphia 76ers, and the Blazers were one of only two teams with the money to give him more than the mid-level exception.
"He is one of the league's ironmen who brings a wealth of veteran leadership to our team and is a great fit for our young and improving roster," Portland general manager Kevin Pritchard said in a statement.
Miller met with Blazers general manager Kevin Pritchard and coach Nate McMillan at a restaurant in Las Vegas earlier this week.
Pritchard said he was impressed with how much Miller know about the Blazers offense.
"Andre was terrific. He knew our team. He knew how he could help our team. He seemed like a coach," Pritchard said.
With Miller, the Blazers get a savvy veteran who excels as a physical, post-up guard.
Miller has played an NBA-high 530 straight games and has missed just three in his career.
"I'm just looking forward to the challenge, you know?" Miller said in a conference call. "I know Portland wants to accomplish a lot of things, and I want to add to that."
Miller went to the Sixers in 2006 in a midseason trade with the Denver Nuggets that involved Allen Iverson. He did not miss a game for Philadelphia.
His departure means the Sixers will likely turn to fourth-year guard Lou Williams to run the point. They made UCLA's Jrue Holiday their first-round pick and hope he can develop into their point guard of the future. Shooting guard Willie Green is the only other true guard on the roster, leaving the Sixers thin in the backcourt.
Before they committed to Miller, the Blazers made a strong push for the Knicks' David Lee, a power forward. On Tuesday night, Blazers coach Nate McMillan and front-office executives Pritchard and Tom Penn had dinner with Lee in Las Vegas to make their recruiting pitch.
One source said the Blazers offered Lee a variety of options, including an opt-out clause that would have made him an unrestricted free agent in the summer of 2011.
But the Knicks and Portland could not agree in discussions Thursday on any kind of a sign-and-trade deal, and the Blazers did not want to risk losing Miller over the seven-day waiting period had they chosen to use their cap space to tender an offer sheet to Lee, which New York would have had the right to match.
Lee, attending Team USA's minicamp in Las Vegas, confirmed the Tuesday night recruiting meeting and said he was intrigued by the possibility of playing for Portland, although he never thought a deal was close.
"At this point it's going to come down to sign-and-trades versus trying to get something worked out with New York," Lee told ESPN.com. "Sign-and-trades, with base-year and compensation and all that stuff, can get complicated. But I think there's enough teams out there that we've had contact with that are excited about trying to get something done that it's a possibility we can do it."
Chad Ford and Chris Sheridan are senior NBA writers for ESPN.com. Information from the Associated Press was used in this report.