Dr. Henry "Hank" Lawson (Mark Feuerstein): A successful New York ER doctor soon to be married to his lovely fiancée, he was dismissed from his job because he triaged a dying teenager before a billionaire hospital benefactor.
He spends the next month in a tailspin of broken engagements and unpaid bills before his brother convinces him to attend a posh party in the Hamptons.
Despite Hank's dislike of the upper class, a potential love interest in local hospital administrator Jill Casey convinces him to become a concierge doctor.
In the fourth season episode "Business and Pleasure", Hank mentions that he graduated from Northwestern University and Mount Sinai School of Medicine.
In Season 8 after Eddie disappears without a word on the day of his marriage to Ms. Newberg, Evan is determined to finally break off any relationship with his father, and it is only through Hank's efforts that they are reconciled.
In the sixth season, Hank offers them his spare room, but Paige and Evan rent a new home and insist that Emma stay with them.
Divya admits that she is practicing medicine without her parents' knowledge, stating that she is unhappy with the degree of control they try to exert over her, the most notorious example being forcing her to marry her childhood friend, an Indian man named Raj Bandyopadhyay.
They accept the news, but still expect her to marry Raj and leave the Hamptons, letting her reveal that she hates the fact that her parents never consider any of her ideas.
In the season finale, after she and Raj are exposed to pneumonic plague, Divya decides to call off her wedding once and for all, as she felt the universe had sent her "one sign too many" that she could not ignore.
Divya eventually moves into a place of her own, only to discover that Raj's parents expect her personally to pay off the expenses they put into the engagement and wedding.
Rather than sell her shares of HankMed to them, as they had intended, Divya takes a part-time shift at Hamptons Heritage to pay off the debt, but the mounting demands on her time juggling both jobs has serious consequences which cause her to resign of her own accord.
In "Bones to Pick" Divya falls down in pain and is rushed to the hospital where she, Hank, Evan, and Paige discover that she has a subchorionic hemorrhage behind the placenta.
She is an executive-level administrator at Hamptons Heritage, the area hospital looked down upon by the elite (who have a running gag stating how it is a death trap or "taco stand"), because it had saved her arm after a teenage surfing accident.
Paige Lawson (née Collins) (Brooke D'Orsay): An upper-class girl who pays Evan to pretend to be her boyfriend while she has a relationship with a much older man.
She engages in many hobbies befitting her high social status including hunting, painting, golf, and surfing, and has a long list of connections she can call upon.
There are some major ups and downs in their relationship and at the end of the second season she invites Evan to join her in a trip to Europe; at Hank's urging he agrees.
In the sixth season, Hank offers his spare room, but Paige and Evan rent a new home and insist that Emma stay with them.
He falls in love with Divya, very early on after he is hired, but she is unaware and it is so difficult to work with her while she's dating Rafa that he leaves to go on a research trip to Iceland.
He, at first, finds it very difficult to share his personal space with her when she tries to add a little homey touch to the kitchen by adding a bouquet of flowers and a throw.
Boris Kuester von Jurgens-Ratenicz (Campbell Scott): A mysterious (seemingly) German nobleman with a large estate in the Hamptons (filmed at Long Island's Oheka Castle).
Boris is somewhat cavalier about experimentation to cure his disease; this has led to unintended side effects such as muscle spasms and temporary blindness from not heeding Hank's advice.
Hank later befriends the young couple, despite a stern rebuke from Tucker's wealthy father, Marshall David Bryant IV.
In Season 3, in the episode An Apple A Day, Hank must treat Libby's mother Elyse (Julie Benz), who has trouble healing from an injury due to scurvy.
Dr. Elizabeth Blair (Marcia Gay Harden): A surgeon and board member at Hamptons Heritage Hospital who is a mentor-turned-adversary to Jill.
Although Hank and Evan are skeptical, it seems that the relationship has a positive effect on Eddie, though Newberg sometimes assumes the persona of an overbearing stepmother.
He attempts to pull some sort of con on Boris, which later turns out to be spying on him for the Securities and Exchange Commission in return for a reduced fraud sentence.
Hank eventually tracks him down (to the Lawson family's old home in Passaic, New Jersey), and Eddie explains that fear and serious medical problems caused his flight.
In the penultimate episode "The Good News Is ...", Hank manages to reconcile them, and Eddie and Ms. Newberg are successfully married and leave for their honeymoon.
Emma Miller (Willa Fitzgerald) is the 17-year-old half-sister of Hank and Evan, the daughter of Eddie and Meredith (a fling from a long time ago).
Viviana eventually leaves the Hamptons to pursue a degree in Tulsa, resulting in a tearful goodbye in front of the local courthouse.