In a White House often accused of being stacked with loyalists, President Obama’s national security adviser said Wednesday there are too many white people in key government posts, endangering national security because they think alike.

Speaking at Florida International University’s commencement, Susan E. Rice, who is black, said a diversified government workforce is more likely to yield “better outcomes” than a predominantly white one.

Referring to criticism that the U.S. national security workforce is “white, male and Yale,” Ms. Rice told the graduates, “In the halls of power, in the faces of our national security leaders, America is still not fully reflected.”

“By now, we should all know the dangers of ‘groupthink,’ where folks who are alike often think alike,” she said. “By contrast, groups comprised of different people tend to question one another’s assumptions, draw on divergent perspectives and experiences, and yield better outcomes.”

Her comments were reminiscent of Supreme Court Justice Sonia Sotomayor, who said in a speech in 2001, before Mr. Obama appointed her to the high court, “I would hope that a wise Latina woman with the richness of her experiences would more often than not reach a better conclusion than a white male who hasn’t lived that life.”

Ms. Rice elaborated in her speech on how having more minorities in the national security field would better protect the homeland.