It marks the ninth time Brady has received the honor, passing retired quarterback Peyton Manning -- an eight-time AFC Player of the Month recipient -- for the most in NFL history.
Brady, 39, led the Patriots (7-1) to an unbeaten 4-0 mark in October while throwing for 1,319 yards and 12 touchdowns against zero interceptions.
He reached the 300-yard plateau in three of those games, including a 406-yard performance against the Cleveland Browns on Oct. 9 -- his first contest after serving his four-game Deflategate suspension.
Since returning, Brady already ranks second in the NFL in yards per game (329.8) and quarterback rating (133.9).
Johnson, 24, led the league in yards from scrimmage in October with 726 (488 rushing, 238 receiving) and tied the league lead for the month with five rushing scores. His 488 yards on the ground ranks third in the NFL.
This is Johnson's first career Player of the Month selection. He was named the league's Rookie of the Month last December/January.
Buffalo Bills linebacker Lorenzo Alexander was tabbed the AFC's Defensive Player of the Month after compiling a league-leading six sacks over five games in the month. Lorenzo, 33, leads the NFL with nine sacks this season.
Atlanta Falcons kicker Matt Bryant earned the NFC honor, going 11-for-12 on field goals with 17 extra points in October. Bryant, 41, joins Morten Andersen as the only Falcons kickers to bring home the award twice.