Brzezinski was born in New York City, the daughter of foreign policy expert and former National Security Advisor Zbigniew Brzezinski and sculptor Emilie Anna Bene?ová, a grandniece of Czechoslovakia's former president Edvard Bene?. Her father was then teaching at Columbia University, but the family moved to McLean, Virginia, near Washington, D.C., in late 1976, when Zbigniew was named National Security Advisor by newly-elected President Jimmy Carter.

Brzezinski attended The Madeira School during her high-school years. She graduated in 1989 from Williams College in Williamstown, Massachusetts, where she majored in English, after transferring from Georgetown University as a junior.

Brzezinski began her journalism career as an assistant at ABC's World News This Morning in 1990. A year later, she moved to Tribune-owned FOX affiliate WTIC-TV/WTIC-DT in Hartford, Connecticut. There, she progressed from assignment and features editor to general assignments reporter. In 1992, she joined CBS affiliate WFSB-TV/WFSB-DT in Hartford and quickly progressed through the ranks to become its weekday morning anchor in 1995. In 1997, she left that role to join the CBS network news, where she served as a correspondent and as anchor for the overnight Up to the Minute news program.

In 2000, Brzezinski began a short hiatus from CBS, during which she worked for rival MSNBC on the weekday afternoon show, Home Page, with co-anchors Gina Gaston and Ashleigh Banfield. She returned to CBS as a correspondent in September 2001, which thrust her into the limelight as a principal "Ground Zero" reporter for the September 11, 2001 attacks. Brzezinski was broadcasting live from the scene when the South Tower collapsed. (Coincidentally, her former MSNBC co-anchor, Ashleigh Banfield, was reporting from Ground Zero for MSNBC.)

In her last position at CBS, Brzezinski served as a CBS News correspondent, substitute anchor, and segment anchor for breaking news segments and routine updates. During this period she was a frequent contributor to CBS Sunday Morning and "60 Minutes."

Brzezinski returned to MSNBC on January 26, 2007, doing the evening "Up To The Minute" news updates. Since then she has anchored primetime newsbreaks during the week, filling in on MSNBC Live weekdays and on the weekends. Brzezinski appears daily as a co-host and news reader on MSNBC's morning program, Morning Joe, with her father as a frequent guest. On Morning Joe, Brzezinski pointed out that she is a Democrat and her co-host, Joe Scarborough is a Republican.

Protesting trivial journalism

On June 26, 2007, near the beginning of Morning Joe, Brzezinski refused to read a report about Paris Hilton's release from jail. One hour later during another news break segment, her producer Andy Jones again pushed the story as the lead, ranking it over Republican Senator Richard Lugar of Indiana's break with President Bush on the Iraq war, which Brzezinski considered more important. After several sarcastic remarks from host Joe Scarborough, she attempted to light the story's script on fire on the air, but was physically prevented from doing so by co-host Willie Geist. She then tore up the script, and one hour later, got up and ran another copy of the script through a paper shredder retrieved from Dan Abrams's office. The incident was quickly popularized on the Internet, and in the days that followed Brzezinski received large quantities of fan mail supporting her on-air protest as a commentary on the tension between 'hard news' and 'entertainment news.' Similarly, on 7-7-10, she spent significant airtime objecting to pressure to report on Lindsay Lohan and Levi Johnston, eventually having Pat Buchanan report the stories with the caption "News You Can't Use."

Brzezinski authored a book, All Things at Once, which was published by Weinstein Books in January 2010. The publisher describes it as "a candid and inspiring motivational book that will help women of all ages confront the unique professional and personal challenges they face in the key moments of their lives."

Since 1993, Brzezinski has been married to TV news reporter James Hoffer, now of WABC-TV. They have two daughters. In her 2010 autobiography, Brzezinski writes about an incident when she fell down the steps of her home while holding her then-4-month-old daughter, breaking the baby's thighbone.