The Trust for Public Land bought Ackerson Meadow earlier this year from private owners for a reported $2.3 million and then donated the land to the national park.
The acreage, Yosemite's largest addition since 1949, lies along the park's western border.
The National Park Service celebrated its 100th anniversary last month. To mark the occasion, President Barack Obama visited Yosemite and spoke about the importance of protecting the land.
The meadow is home to many species of plants and animals, and park officials have labeled it as vitally important.
"The purchase supports the long-term health of the meadow and its wild inhabitants," an official said.
Park officials said meadows take up only 3 percent of the national park's land but are home to about one-third of the park's plant species.
Yosemite celebrated its 125th anniversary last year. The official said the original plans for Yosemite included Ackerson Meadow and that "it is exciting to finally have this important place protected."