Biden interjected to say that his agents were "excited" Pierson had been selected.
Earlier Wednesday, White House spokesman Josh Earnest defended Pierson's selection after a report in The Washington Post suggested her pick provoked resentment from rank-and-file agents who felt she had spent relatively little time in the field.
The paper anonymously quoted one agent who complained that Pierson had not "done her time in the trenches" and in recent years had "mostly been riding a desk."
Earnest said Pierson's "experience in human resources and training" would help the agency as it works to repair its reputation in the aftermath of the Colombian prostitution scandal that led to the dismissal of six agents.
The president reiterated Wednesday that he had full confidence in his selection.
“She has extraordinary qualifications, and I think a lot of people who have worked with Julia know how dedicated, how professional, how committed she is," Obama said, adding he was "certain that she’s going to thrive in this job."