At 19, Davis began his career with a second round TKO of Luis Guzman in April 1993 and compiled a professional record of 17–1–2 over the next seven years on the New England circuit, where he fought primarily as a Junior-Middleweight.

Coming in with reputed boxing skills, he picked Joe Stevenson in episode four in what proved to be a mismatch as Davis was quickly taken down by the eventual winner and submitted.

Following the series, Davis strongly considered retirement but recuperated from a shoulder injury picked up against Joe Stevenson and went back to MMA training.

Davis subsequently bounced back with 11 wins, including a triumphant return to the UFC at Ortiz vs. Shamrock 3: The Final Chapter.

His next fight was a highlight-reel knockout win against fierce rival Jess Liaudin at UFC 80 in Newcastle, England.

He suggested that the fight take place in Ireland, where Davis had gained a substantial following due to his emphasis on his Irish roots.

Leading up to the event, both fighters promised to stand and trade blows for the entire fight, rather than engage in grappling.

Hardy called Davis a "fake Irishman" as well as a "Plastic Paddy" and said his website "looked like a St. Patrick's day parade had blown up".

Davis lost to Nate Diaz on August 28, 2010, at UFC 118 via technical submission (guillotine choke) in the third round.

[16] In an interview with MMA Junkie.com Davis confirmed he would drop to the Lightweight division for his next UFC appearance and said he made the decision after the realization that his frame is better suited for 155 pounds.

Davis returned at MFC 30, defeating Pete Spratt by unanimous decision in a rematch of their bout from UFC 69.

[22][23] Davis fought Ultimate Fighter 13 alumnus Chuck O'Neil in a Welterweight bout at W-1 Reloaded in Miami, Florida, on October 15.

[27] On May 6, 2012, Davis turned his hand to kickboxing to challenge Mark Casserly for the ISKA World Light Cruiserweight (-84.6 kg/186.5 lb) Oriental Championship in Dublin, Ireland, losing by head-kick knockout in round one.

[28] Davis replaced Karo Parisyan and faced David Bielkheden at Superior Challenge 8 on October 6, 2012, in Malmo, Sweden.

Following his loss to Alexander Sarnavskiy, Davis faced Ryan Sanders at NEF: Fight Night 12 on February 8, 2014.

[33] The bout ended in a no contest when Davis hit Spiritwolf with an inadvertent knee to the groin in the first round and he could not continue.

[34] On July 21, 2020, news surfaced that Davis is expected to face Nick Alley at Premier FC 31 on October 3, 2020.

and at the Lockdown pay-per-view event in April 2008 as Samoa Joe's personal trainer for his TNA World Heavyweight Championship match against Kurt Angle.