Mark Wahlberg began training for the role in 2005. Throughout the various production delays, Wahlberg continued to train every day so that he could be ready for filming. Filming finally began in July 2009.
Having David O. Russell to direct the film was Christian Bale's suggestion. At first Mark Wahlberg was uncomfortable of calling his friend to do it after the harrowing experience of working in Three Kings but relented when Bale stated that he wanted to work with Russell.
Major studios in Hollywood declined to finance this movie but because of Paramount's enthusiasm of the material, the studio executed a right of first refusal. The script then ended up at producer Ryan Kavanaugh who then reworked it to make it more accessible and family-friendly (Kavanaugh self-funded the $25 million movie including the marketing campaign). When it came to the distribution stage, Paramount beat three other studios in a bidding contest for video and theatrical distribution.
Micky Ward's real life trainer Mickey O'Keefe was asked to appear as himself in the film, but turned the role down since he had never acted before. Mark Wahlberg told him he would be able to since he was a cop and therefore he has to act and think fast on his feet. This was convincing enough and he took the role.
The young man who rushes into the restaurant to warn the Eklund-Ward family that Dicky is being beat up by the cops, is actually Sean Eklund, nephew of the real Micky Ward and Dicky Eklund and became New England Lightweight boxing champion in 2010.
Christian Bale spent hours of time with the real Dicky Eklund to learn how to emulate him properly. He had to lose 30 pounds of weight because Eklund was a crack addict at the time. Director David O. Russell said it was much more than mimicry. He remarked: "Dicky has a rhythm to him, a music. Christian had to understand how his mind works."
According to Micky Ward, he and Dicky Eklund were to have sizable cameos in a scene together. But Eklund disliked his lines and refused to say them so the scene was not filmed. Ward appears briefly as a spectator in the fight against Hernandez.
Dicky Eklund's nickname was actually spelled "Dickie" in real life. Eklund requested for it to be spelled "Dicky" in the film so that it would match Micky Ward's name. After the release of the film, Eklund and his son, 'Dicky Eklund Jr' began using this spelling.
Dicky Eklund did not like how his mother and sisters were portrayed in the film. He yelled at Christian Bale after a screening in anger. His sisters also did not like their portrayals. Beaver Eklund walked out of a screening of the film in protest.
According to Bianca Hunter, Melissa Leo and Christian Bale stayed in character on the set even when they were not filming. Hunter also said that the real Pork Eklund was on the set and told Hunter that she did not like how she was being portrayed.
During the 2011 Academy Awards awards campaign, Melissa Leo financed and took out her own "For Your Consideration" ads for a Best Supporting Actress nomination; a first in Hollywood. The publicity move was viewed controversially among many industry insiders, but it ultimately paid off for Leo, who not only was nominated, but won the Oscar.
The trivia items below may give away important plot points.
In the ending fight between Micky Ward and Shea Neary, announcer Jim Lampley says "Ward nods as if to say, 'C'mon, c'mon let's fight!... Just imagine if you'd bought a ticket" ... these two lines are taken directly from Lampley's commentary in the 9th round of the May 18th, 2002 fight between Micky Ward and Arturo Gatti.
The interviews in the beginning and the end were improvised by Christian Bale and Mark Wahlberg, while in-character. They were done late night with only Bale, Wahlberg and director David O. Russell present. Bale actually became emotional and left the couch.
The police officer who jokingly arrests the real life Dicky Eklund at the end of the movie, during the credits, is actually Lowell police officer, Eric Wayne. Eric's father, Gerald Wayne, was the actual police officer who arrested the real life Dick Eklund after his robbery shenanigans in the early 1990s, which were depicted in The Fighter. Dick Eklund and Gerald Wayne actually maintained a mutually friendly relationship before, during and after the arrest.