The official unemployment rate for those ages, released by the Department of Labor, was 10.9 percent in November, the group Generation Opportunity said.
But adding in more than 1.7 million more workers no longer counted in the data, because they have stopped looking for work due to the lack of jobs brings the unemployment rate up to 16.4 percent, the group said.
"Today's unemployment picture for millennials offers little in the way of promise for a generation in which genuine opportunities continue to be few and far between," said senior vice president for communications at Generation Opportunity, Matthew Faraci.
"Millennials have high expectations of those who were elected in November and are eager for the kind of real job growth that would finally, after years of stagnation, afford them a chance to put their substantial skills to work," he said in a statement.
Generation Opportunity said the unemployment rate for 18-29 year old African-Americans in November was 18.5 percent. For millennial Hispanics it was 12.5 percent. For women in that age group it was 10.5 percent.