The president, along with wife Michelle Obama and daughter Malia, joined other volunteers at Browne Education Center in Washington.
During brief remarks, the president said there was no better way to honor King than to do something on behalf of others. He also acknowledged the controversy surrounding a quote on the new MLK memorial in Washington, which is being changed amid criticism that it did not accurately reflect King's words.
"What he really said was all of us can be a drum major for service, all of us can be a drum major for justice," Obama said. "There is nobody who can't serve, nobody who can't help somebody else."
The inscription on the King memorial, located on the National Mall, currently reads: "I was a drum major for justice, peace and righteousness." The phrase is modified from a sermon known as the "Drum Major Instinct", which King delivered just two months before he was assassinated in 1968.
In the speech, King's words seem more modest than the paraphrased inscription: "Yes, if you want to say that I was a drum major, say that I was a drum major for justice. Say that I was a drum major for peace. I was a drum major for righteousness. And all of the other shallow things will not matter."
After meeting with volunteers, the Obamas headed to the school library to help build bookshelves and a reading corner for students. The president and first lady were then put to work painting two King quotes on the library walls.
The president stood on a chair and carefully used blue paint to write the phrase "The time is always right to do what is right." Mrs. Obama painted the words "I have a dream."
This was the third year in a row the Obamas have participated in a service project on the King holiday.