In the vibrant Northside of Dublin, Ireland, young music enthusiast Jimmy Rabbitte dreams of managing a band that embodies the spirit of 1950s and 60s African-American soul and rock and roll. Motivated by this vision, he takes the initiative to post an advertisement in the local newspaper and hosts auditions at his family's home. Amid a wave of unsuitable candidates, Jimmy decides to form a band with his friends and other individuals he meets along the way. The lineup includes charismatic lead singer Deco Cuffe, talented guitarist Outspan Foster, skilled keyboardist Steven Clifford, alto saxophonist Dean Fay, bassist Derek Scully, drummer Billy Mooney, alongside strong female backup singers Bernie McGloughlin, Natalie Murphy, and Imelda Quirke.
A twist of fate introduces him to Joey "The Lips" Fagan, an experienced trumpeter with wild, entertaining tales of famous musicians. Inspired by Joey’s stories, he dubs the band "The Commitments."
To kickstart their journey, Jimmy purchases a drum set and transacts for a piano from Steven's grandmother. He also acquires the remaining instruments from Duffy, a dealer operating in the shadows of the black market. The group begins to rehearse diligently above a local snooker hall, and their hard work pays off when they convince a church community center to host a gig, cleverly disguising it as an anti-heroin campaign. To keep an eye on the rowdy band, Jimmy enlists Mickah Wallace, a tough and fiery bouncer, as their security.
Their debut gig attracts a sizable crowd, but chaos ensues when Deco accidentally strikes Derek with his microphone stand, resulting in a disastrous power outage caused by exploding amplifiers.
As the band navigates the pressures of fame and personalities clash, Joey finds himself in romantic entanglements with Natalie, then Bernie, and Imelda, while Deco's egotism drives him to overshadow the others with his inflated sense of stardom. During a performance at a different location, Billy's accidental mishap with the cymbals sparks an argument with Deco, leading Billy to leave the group behind, further complicating Jimmy's plans.
At their next gig at a roller disco, faced with Duffy's demands for payment, Mickah erupts in a violent confrontation, kicking Duffy out. As Jimmy introduces the band with a flourish, they receive a thunderous cheer from the audience.
With hopes high, Joey tantalizingly hints that he can bring the legendary Wilson Pickett to join them. Eager for the spotlight, Jimmy convinces a group of journalists to cover their upcoming show. Though the venue fills with excited fans, backstage drama ensues as band members bicker, casting doubt about Pickett's participation. Ultimately, they take the stage, and Deco's outburst marks the peak of tension. Yet, their rendition of Pickett's classic, > "In the Midnight Hour," hushes the crowd, reclaiming the energy.
Post-performance, confrontations escalate, and in a swinging storm of frustration, Jimmy declares the band is done. Just when it seems everything is lost, Joey steps outside with Jimmy, who chastises him for misleading them about Pickett. In a twist of fate, Pickett's limo pulls up, confirming that Joey's claims were indeed true, albeit just too late.
In a reflective finale, Jimmy shares how the band members went in different directions after their journey: Bernie joined a country band, Deco pursued a record deal and his growing ego, while Mickah embraced punk music. Outspan and Derek found solace in street busking, Dean transitioned to jazz, and Joey even sent a postcard from his tour that sparked intrigue. Meanwhile, Steven became a doctor but misses the thrill of performing, Billy is recovering from an unfortunate horse-related incident, Imelda’s marriage cut short her singing dreams, and Natalie has found success as a solo artist. Ultimately, there’s an implication of romance brewing between her and Jimmy as their paths diverge but remain intertwined.
