It happened around 3:45 p.m. Tuesday at Central Park West and West 86th Street.
The branch struck the woman as she walked along a path in the park.
The victim, 59-year-old Sharon Reese, a tourist from Terre Haute, Indiana is in serious but stable condition at St. Luke's Roosevelt Hospital.
The tree came down from about 40 feet above the ground.
"I saw a woman lying on the ground. She had a bandage wrapped around her head, a giant branch on the ground," said witness Penelope Clark.
Workers dragged the tree away from the scene.
Incidents like this happen more often than you might think, with some victims hospitalized,or worse.
3 years ago, a man was killed in the park by a snow-covered branch.
And later that same year, a 6-month old baby was killed and her mother injured by a falling tree branch at the Central Park Zoo.
Lawsuits have forced the city to reportedly pay out millions to victims over the years, a number that continues to rise.
"We expect every tree in New York City to be properly inspected and maintained," said Geoffrey Croft of the watchdog group New York City Park Advocates.
But some park-goers believe that's unrealistic.
"They can't check every single tree every day," said Beate Echols.
With another victim in the hospital, it is a growing debate about a park millions of New Yorkers worship, and others see as a potential growing liability.