She is married to screenwriter Daniel Zelman, and on April 7, 2004, gave birth to their son, Roman Walker Zelman. She became widely known as interior designer Grace Adler in the sitcom Will & Grace. In 2003 she won an Emmy Award for Best Actress in a Comedy Series for the role.
Messing was born into a Jewish family in the New York City borough of Brooklyn. When she was three she moved with her parents and her older brother, Brett, to a quiet town outside Providence, Rhode Island. Her father, Brian Messing, is a sales executive for a jewelry manufacturer; her mother, Sandy Messing, has worked as a professional singer, banker, travel agent, and real estate agent.
As a youngster Messing took lessons in dance, singing, and acting. While Messing's parents encouraged her dream of becoming an actress, they also urged her to get a liberal arts education before deciding on acting as a career. Heeding their advice, she attended Brandeis University, in Waltham, Massachusetts. During her junior year she studied theater at the prestigious British European Studio Group of London program, in England, an experience that fueled her desire to act.
After graduating summa cum laude from Brandeis in 1990, with a bachelor's degree in theater arts, Messing gained admission to the elite Graduate Acting Program at New York University (NYU), which accepts only about 15 new students annually. Three years later she earned a master's degree in fine arts from NYU.
Later in 1993, Messing won praise for her acting in the pre-Broadway workshop production of Tony Kushner's much-lauded play Angels in America: Perestroika. Before long, she broke into television by appearing on the award-winning series NYPD Blue, playing the part of Dana Abandando—the conniving sister of one of the show's main characters. Those installments aired in late 1994 and early 1995.
In 1995, Messing made her film debut with a small role in A Walk in the Clouds, a love story directed by Alfonso Arau. She appeared as the wife of a World War II veteran played by Keanu Reeves. This exposure led the Fox network to make her the co-star of the television sitcom Ned and Stacey. The series, about a young man and a young woman who marry for reasons other than love after knowing each other for only a week, lasted for two seasons (1995–1997).
Around the same time, Messing appeared as Jerry Seinfeld's date in two episodes of the hit television show Seinfeld: "The Wait Out" in 1996, and "The Yada Yada" in 1997. The actress turned down a starring role in another television sitcom to appear in Donald Margulies's two-character play Collected Stories, which opened at the Off-Broadway Manhattan Theater Club in 1997. Messing portrayed the protégé and, ultimately, literary betrayer of a famous short-story writer (Maria Tucci).
In 1998 Messing had a lead role as the bioanthropologist Sloan Parker on ABC's dramatic science-fiction television series Prey. Meanwhile, Messing's agent had approached the actress with the pilot script for the television show Will & Grace, Messing was inclined to take some time off, but the pilot for Will & Grace intrigued her.
Messing was hand-picked by Woody Allen for a small role in his 1998 movie Celebrity. In an interview later, Messing described the method Allen used to enable her to discover the essence of her character, one that resulted in nerve-racking uncertainty for the actress, who during her first four days on the set got no feedback from Allen. After he offered his first words of guidance, on the fifth day, Messing felt herself undergoing a transformation.
Messing met her future husband Daniel Zelman, an actor and screenwriter, on their first day as graduate students at NYU. She and Zelman, who were married on September 3, 2000, live in Los Angeles, California.