The endorsement comes as a surprise given the right-leaning views of the Post, owned by media magnate Rupert Murdoch.
Clinton won her Senate seat in 2000 despite a concerted effort by the Post to attack her candidacy. The Post even ran a pleading headline, "Don't Run!" before Clinton formally joined the race.
During Bill Clinton's last year in the White House, the Post's news pages frequently referred to him as "horndog-in-chief."
"Surprised? Well, so are we — a little," said the editorial in the Post, which has a generally right-leaning editorial page. "But, then, there really isn't much of a choice in this race."
And what about Clinton's reported White House aspirations?
"...We think she's done such a good job these last six years that she'd do well to serve six more. If not 12," said the Post. "Re-elect Hillary. In 2012."
In addition to the Post, News Corp., the global media conglomerate controlled by Murdoch, owns Fox News and other television networks, as well as The Times of London and many other British and Australian newspapers.
Despite the general conservative slant of Murdoch's media, hein July, which was "a shock to both his right-wing allies and his liberal enemies," according to The New Yorker.
The Post seems to have been kinder to Clinton recently.
"Well, New Yorkers simply expect their major officeholders to be presidential aspirants — and the pols always rise to the bait (occasionally delivering ludicrous results; has anyone seen George Pataki in New York lately?)," the Post editorial read.
"So Hillary's caught the bug. So what?"