With the Marine Band providing the music, the president and first lady Michelle Obama hosted the picnic for members on the South Lawn of the White House.
"I want to say a special welcome not only to the members of Congress, but most importantly to their families," the president said, getting a laugh when he added, "because Michelle reminds me every day how difficult it is to be married to a politician.
"And the sacrifices that all of you make -- the birthday parties that get missed, or the soccer games that you're late to, the travel that keeps you away from your loved ones -- all of that obviously is in service of our country," he said. "So we're thrilled that you have at least one day where you got a chance to be together in Washington and nobody is arguing."
The president said the get-together was a reminder that "for all the political differences that are sometimes expressed in this town, we are first and foremost Americans -- not Democrats or Republicans."
"And I think all of us want to make sure that during extraordinarily challenging times for this country that we constantly keep that in mind," he said. "That's what the people who sent us here are expecting."
The president told the members of Congress he looked forward to "continuing to work with you."