Kearns, who had two hits, leads the Marlins with nine RBIs this spring. The veteran is a non-roster invitee who is battling to earn a job as a right-handed bat off Miami's bench.
Ricky Nolasco worked 6 1/3 innings -- the longest outing for a Marlins starter this spring -- allowing one run with four strikeouts. The right-hander effectively pounded the zone, throwing 60 of his 83 pitches for strikes.
Gio Gonzalez, the Nationals' No. 2 starter, settled down after a rough first inning. The left-hander, who grew up in Miami, gave up three runs on seven hits with six strikeouts in five innings. He threw 81 pitches, with 53 strikes, while walking one.
After Nolasco worked through the first inning on four pitches, the Marlins responded with three quick runs off Gonzalez.
Jose Reyes opened the first with an infield single, and he stole second. With one out, Hanley Ramirez walked and Gaby Sanchez delivered an RBI single. Kearns made it 3-0 with a two-out, two-run double to left.
Nolasco held the Nationals scoreless until Roger Bernadina lifted an RBI single to center in the sixth. Mark DeRosa, who singled to open the inning, scored from second.
Nolasco's afternoon ended in the seventh after he retired Ian Desmond on a lineout to third.
Up next: The Nationals will travel to take on the Mets in Port St. Lucie on Wednesday at 1:10 p.m ET. Right-hander Jordan Zimmermann will make his fifth start for Washington this spring, as he tries to end camp on a high note. Zimmermann has allowed eight earned runs in 15 2/3 innings, but he's had a pair of scoreless outings.