The 38-year-old American has been struggling for weeks with back spasms and pain and said Tuesday he will not defend his title at this week's $6.2 million Arnold Palmer tournament.
"It's too early to know about the Masters and I will continue to be evaluated and work closely with my doctors," Woods said on his website.
"Unfortunately, my back spasms and the pain haven't subsided. I personally called Arnold today to tell him that, sadly, I won't be able to play in his tournament this year.
The Masters runs from April 10 to 13.
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Woods, a 14-time major champion chasing the all-time record of 18 won by Jack Nicklaus, has not won a major since the 2008 US Open.
But his injury woes are mounting and he withdrew during the final round of the Honda Classic three weeks ago because of the back problem and has made just four starts this season.
His best finish is a tie for 25th place at the WGC-Cadillac Championship two weeks ago.
"I am certainly sorry that Tiger is not able to play," Palmer said. "Quite obviously, we will miss having him here this week. He called me to tell me that his back was still giving him a lot of trouble and he didn't feel he should play.
"I told him I understood and wished him well."
Woods claimed his second consecutive Arnold Palmer title last year, becoming only the second player to win the same tournament eight times after Sam Snead, who won eight Greater Greensboro Open titles.