CastWilliam H. Macy as Frank GallagherFather to the six Gallagher children. He is a selfish alcoholic and completely narcissistic, and has done nothing but collect his disability checks (illegally) and drink heavily for years. He begins a relationship with Sheila after he discovers she gets maximum disability benefits for her agoraphobia. Although he is Fiona, Lip, Debbie, Carl, and Ian's biological father, he is not Liam's. He often self-righteously pontificates about political and social issues, yet spends most of his time developing schemes to cheat the system and take advantage of others in order to make money. He pays little attention to his children, but occasionally displays care and concern for them in drastic circumstances.
Emmy Rossum as Fiona GallagherThe eldest of the Gallagher children (21). Because of her mother's absence and Frank's neglect, most of the responsibility of child-rearing falls on her shoulders; this forced her to drop out of high school in her junior year. She works a few dead-end, minimum wage jobs to bring in money and support her five siblings. Though often stressed out and exhausted by her responsibilities, she never fails to perform them. She is prone to being overly selfless, and sometimes needs to be reminded to look out for her own happiness as well as that of her siblings. At the close of season two she does get her GED and begins to take interest in more serious jobs.
Justin Chatwin as Steve Wilton/Jimmy LishmanA young man relentlessly pursuing Fiona, going to great lengths to win her over. He owns expensive things and throws money around liberally, which Fiona finds off-putting, until she discovers he steals cars for a living. It is later discovered that his real name is Jimmy, and he comes from a wealthy family.
Jeremy Allen White as Phillip "Lip" GallagherThe second Gallagher child (17) and the most academic. He is a straight A student. He uses his intelligence in various odd jobs to make money, such as running an ice cream truck in the summer that sells beer and marijuana, or taking the SATs for fellow students (often scoring a 2400, a perfect score). Despite his above average intelligence, he is not considered responsible, and is frequently shown smoking cigarettes, using marijuana, drinking alcohol, and having unprotected sex. He has a strong bond with his younger brother Ian, and is the first family member to know that Ian is gay. Lip develops a torrid relationship with Karen after helping her in math, and soon falls in love with her.
Cameron Monaghan as Ian GallagherThe third Gallagher child (16) and (according to Frank) the most like their mother. He participates in Army ROTC at school and works at a local grocery store. He is gay, but only a handful of people (Fiona, Frank, Jimmy, Monica, Mickey, Mandy, and Lip) know about it. He had a furtive gay relationship with the Muslim grocer, Kash, his employer. He is currently pursuing a relationship with Mickey Milkovich. He is not Frank's son, but of Monica and one of Frank's brothers. His middle name is Clayton.
Emma Kenney as Debbie GallagherOne of the middle Gallagher children (11), Debbie is kind, helpful, and has a good heart. She's willing to bring her baby brother to school for show and tell when there's no one else to watch him, put a pillow under her father's head when he's passed out on the floor, and collect money for charity year round – only some of which she keeps for herself.
Ethan Cutkosky as Carl GallagherThe second youngest Gallagher child (10). He shares a room with older brothers Lip and Ian, who try to keep their more adult interests from him. Carl is often in trouble at school for attacking other students. He shows several psychopathic tendencies such as mutilating his toys and bringing stray animals home and killing them. He also plays football on the team that Steve coaches.
Brennan Kane Johnson & Blake Alexander Johnson as Liam GallagherThe youngest of the Gallagher children (2), he is black despite having two white parents.