The White House did not offer any details on why Trump would not speak to the 108-year-old civil rights group.
"My understanding is that the invitation has been declined for this year," Sanders told reporters at a briefing.
She said that while Trump would not speak at the conference, the White House would be happy to have a dialog with the group.
"We would certainly like to be able to continue to do that," Sanders said.
The NAACP did not immediately respond to request for comment.
Trump had declined to speak at the NAACP convention last year because it coincided with the Republican National Convention in Cleveland, where he was formally nominated as the party's presidential candidate. Previous Republican presidential nominees regularly attended the annual meetings of the oldest U.S. civil rights organization.
Trump's most recent predecessors in the White House, Barack Obama, a Democrat, and George W. Bush, a Republican, both delivered speeches to the NAACP during their time in office.
This year's NAACP convention begins Saturday in Baltimore.
During his campaign, Trump pledged to improve the lives of black Americans, who voted overwhelmingly in favor of his Democratic opponent, Hillary Clinton, in the 2016 presidential election.
Trump has been criticized by some groups, including the Congressional Black Caucus, for not doing enough to address issues in the African-American community.