McMahon penned his loan move to the Bantams this Thursday (emergency loan deadline day) at the Coral Windows Stadium, with the experienced campaigner signing with City until the end of the 2014/2015 campaign.
McMahon, who turned 29 on Tuesday, has played 33 times for the Tangerines this season in the Championship and becomes the third player to move to the Bantams from Bloomfield Road following similar loan moves for Gary MacKenzie and Francois Zoko.
Fresh from signing for Phil Parkinson's side, McMahon will now come into contention for Saturday's home fixture with Oldham Athletic.
City's latest signing will also wear squad number 29 during his time at the Coral Windows Stadium this season.
McMahon, who has captained Blackpool on numerous occasions this season, can feature in a number of positions on the pitch including right back, centre back and central midfield. He is also handy at dead-ball situations and has a number of goals and assists to his name from set-pieces.
Having come through the ranks at Middlesbrough, McMahon featured in the same youth team as Andrew Davies, Gary Liddle and Jason Kennedy that reached the F.A Youth Cup Final two years on the trot during the early 2000's.
Turning pro shortly after captaining 'Boro to F.A Youth Cup victory over Aston Villa in 2004, McMahon made his senior debut with the first team in a 1-1 draw against Manchester United at Old Trafford.
McMahon would also go on to see action in the UEFA Cup (now Europa League) as well during his debut season as a professional for Middlesbrough.
The Bishop Auckland-born player featured 137 times in total for Middlesbrough - plus a handful of appearances while on loan at Blackpool and Sheffield Wednesday - before eventually leaving the Riverside Stadium in 2012.
McMahon moved to Sheffield United for the start of the 2012/2013 season and helped the Blades into the League One Play-Offs in his first full year at Bramall Lane.
He was a regular in United's line up the following year - 2013/2014 - before earning a move back into the Championship with Blackpool in January 2014.
Along with a large number of appearances under his belt at domestic level, McMahon has also been capped internationally with England at Under 16, Under 17 and Under 19 level.
In other news, Oliver Burke has now returned to Nottingham Forest following the completion of his one-month loan from the City Ground.
Burke played for City in the games away to Swindon Town and Peterborough United at the end of last month during his brief spell with the Bantams.