The deal is pending a physical and has yet to be confirmed by the Red Sox, but an MLB.com report on the transaction is posted on the team's website.
Napoli has played catcher for most of his seven-year career, which includes five seasons with the Angels and the most recent two with the Texas Rangers, but is expected to play first base for the Red Sox. He has started 118 games at that position.
His best season came in 2011, when he hit .320 with 30 home runs and 75 RBIs to help the Rangers win their second straight American League pennant. Those numbers took a downward turn last season, as he hit . 227 with 24 home runs and 56 RBIs.
Still, he stands a good shot at bouncing back playing at Fenway Park, where he is a .307 hitter with nine home runs and 20 RBIs in 75 at-bats.
Napoli has a career average of .259 with 146 homers and 380 RBIs.