Woods, 38, who won this tournament at Bay Hill a year ago for the eighth time, tweeted the news and also announced it on his website.
"Called Arnold today to tell him that sadly I won't be able to play," Woods said on his website. "Back spasms and the pain haven't subsided.
"It's too early to know about the Masters, and I will continue to be evaluated and work closely with my doctors. I feel badly that I won't be able to play in this great tournament this week."
Woods withdrew from the Honda Classic after 13 holes on March 2 and then struggled for a good part of the WGC-Cadillac Championship at Doral the following week. A day after shooting 66 at Doral, Woods aggravated his back problems during the final round on March 9 when he attempted hit a shot out of a bunker due to an awkward stance. He went on to shoot 78 -- his highest final-round score as a pro -- and failed to make a birdie during the final round for just the eighth time in his career.
Afterward, Woods said the injury and pain were the same as what bothered him a week earlier at the Honda Classic.
"If it flares up, it flares up," he said. "It's just a matter of keeping it calm, and we had a quick turnaround here from last week. It would be nice to have a week off where I can shut it down and get some treatment."
But not even that was apparently enough for Woods to play at a place where he has won eight times in 16 starts as a pro. Attempts to get more information about Woods' condition have been unsuccessful.
At Doral, Woods was asked if the injury was more serious than back spasms: "Well, it is back spasms, so we've done all the protocols and it's just a matter of keeping everything aligned so I don't go into that."
Asked if he has had an MRI performed, he replied: "As I said, we've done all the protocols."
Woods has had several injuries throughout his 18-year career, the most serious a knee problem that required ACL surgery in 2008, knocking him out of action for more than eight months. He missed two major championships that year. He also missed two majors in 2011 when he dealt with knee and Achilles problems that sidelined him for four months.
Last year, Woods' elbow bothered him at the U.S. Open, causing him to withdraw from the AT&T National, a tournament that benefits his foundation. And then at the Barclays in August, Woods had back spasms that sent him to the ground during the final round. He ended up finishing tied for second, but struggled throughout the rest of the FedEx Cup playoffs.
Although he came back and tied for third at a European Tour event in Turkey and lost in a playoff at the World Challenge, Woods took care in the offseason, he said. He played and practiced little in anticipation of a long year.
"I took a lot of time off this winter to get ready for the season because it's going to be a long grind," he said last month.
And yet, three tournaments in, the back problems surfaced again and would appear still be an issue. Woods is off to the worst start of his career, with a tie for 80th at the Farmers Insurance Open, a tie for 41st at the Dubai Desert Classic, the withdrawal from the Honda Classic and for 25th at Doral.
The Bay Hill event was expected to be his last tournament prior to the Masters, which begins in three weeks, on April 10. In each of his four Masters victories -- the last in 2005 -- Woods won at least once prior to getting to Augusta National.
The only time Woods played less going into the Masters was in 2010, when he made his first start at the Masters and tied for fourth just months after his off-the-course scandal shocked the golf world. In 2009, Woods played three times prior to the Masters and tied for sixth.