She unveiled a shorter, above-the-shoulder bob on Tuesday, when she accompanied U.S. President Barack Obama to Wilmington, Del., to attend the funeral of Vice-President Joe Biden's 92-year-old mother, Jean.
At least five centimetres of Mrs. Obama's dark locks have been sheared off.
Mrs. Obama tried to minimize the buzz her new do would set off by telling reporters Wednesday that it was just "a little cut," unworthy of being newsworthy. But as with other first ladies before her, any clothing or hairstyle change is noticed and talked about.
Remember Hillary Rodham Clinton's ever-changing hairdos during her husband Bill Clinton's White House years?
When Mrs. Obama attended a country music event at the White House last July with her hair pinned up, it sparked a flurry of commentary and speculation on the Internet and elsewhere about whether she'd surprised everyone and had it cut.
The first lady had allowed her hair to grow longer last year. Since November, she wore it mostly in an updo, tucked under or pulled into a tight bun, as she did when she returned to the White House on Jan. 4 after the family's holiday vacation in Hawaii.
The haircut was sometime between her return and Tuesday.
Mrs. Obama's office had no comment Wednesday on why she shortened her hair. But at least two special occasions are approaching. Mrs. Obama turns 46 on Sunday, and next Wednesday marks the couple's first year as president and first lady.