Matthews, an undrafted free agent out of Marquette readying for his second year in the NBA, averaged 9.4 points and 2.3 rebounds in 24.7 minutes for the Jazz last season as a rookie. He appeared in all 82 games last season and started in 48.
The Blazers held a news conference to announce the deal Wednesday morning at a park near the Rose Garden Arena.
Matthews was immediately hit with a question about the size of his front-loaded deal, the largest he could get as a second-year player.
"A lot of people respected what I did because of how hard I played, how hard I went. That wasn't to get a big contract like this. This big contract helps my family out. I'm all right as long as I can play this game. So people that say I'm overpaid, I might be. We never know. I know one thing, I will be in the gym and I will be working to give myself a chance to be the best I can be."
The deal with Matthews was all but inevitable after the Jazz signed Raja Bell on Monday to a three-year deal worth a reported $10 million.
"As only a first-year player last season, he demonstrated a lot of maturity and ability. He's already one of the best young defenders in the league and offensively he's an emerging threat," new Blazers general manager Rich Cho said in a statement. "He's going to add a lot of versatility to our roster."
Matthews was something of a longshot when he joined the Jazz in training camp last season, but he eventually became a starter. In the postseason, he averaged 13.2 points and 4.4 rebounds in 37.1 minutes per game. He started all 10 of Utah's playoff games.
"I really need to thank the Utah Jazz for giving me this opportunity to live my dream out and became an NBA player," he said Wednesday.
Blazers coach Nate McMillan has said he could see Matthews in the role of small forward or shooting guard. Matthews said he'll play wherever the Blazers want him.
"I'm going to play hard. I'm going to work hard. Whether it's backing up Brandon (Roy) or playing alongside Brandon. I'm not sure. That's what training camp is for, that's what preseason is for. I know they have a plan for me, and I know I have a plan for myself, and that's to get better and help this team get better."
The deal for Matthews comes just two days after the Blazers appointed Cho as their new general manager.
Cho, who replaces Kevin Pritchard, was an assistant GM with Seattle/Oklahoma City for the past nine seasons. He is highly regarded for his expertise with the salary cap and the collective bargaining agreement. He's also got scouting experience.
Pritchard was dismissed in the hours before last month's NBA draft.
Michael Born, Portland's director of NBA scouting, and Chad Buchanan, director of college scouting, took over Pritchard's duties while the search for the GM was on. The offer for Matthews was made under their watch.
Portland was the only team Matthews visited, although his agent entertained interest from other teams, he said.
Matthews said he was impressed with what Portland was able to accomplish last season despite a spate of injuries. The Blazers went 50-32 last season and made the playoffs.
"A lot of people wrote Portland off. But they had a lot of heart, a lot of toughness," he said. "And I'm just hoping I can bring that and I can add that."