Harper was benched by Nationals manager Matt Williams on Saturday for failing to run hard to first base.
"He knows he was wrong," Trout said of Harper.
Trout, the 2009 Millville High School graduate who has become the face of major-league baseball, spoke with Harper for about 10 minutes during batting practice Monday. The two were teammates in the Arizona Fall League in 2011.
"Talking baseball," Trout said.
Trout was 2 for 5 as the Angels earned a 4-2 victory. Harper was 0 for 3.
Trout and Harper are linked by their status as two of the most highly touted young players in the game and also because they were called up to the major leagues for good on the same day: April 28, 2012.
"Maybe 20 years from now, some kid will say, 'I was at a game and saw Bryce Harper and Mike Trout on the same field,' " Angels manager Mike Scioscia said.
There were many more Harper jerseys than Trout jerseys in the stands on a warm night in the nation's capital.
But Trout was proudly represented by several folks from Millville, including his parents, Jeff and Debbie, and some other family members - most of whom were wearing red No. 27 jerseys with "Trout" on the back.
"It's hectic but it's all good," Jeff Trout said before the game.
Mike Trout said the 15 tickets he left for family and friends were his most ever at a road game.
He's certain to top that when he plays against the Phillies at Citizens Bank Park on May 13-14 in a short interleague series.
Trout, a diehard Eagles fan who still wonders what was behind his favorite team's decision to release wide receiver DeSean Jackson, also grew up a Phillies fan.
"I was a [Chase] Utley fan," Trout said. "And [Jimmy] Rollins, of course, because I was a shortstop."
Before batting practice, Trout met on the field with three generations of fans from his hometown - Ron Noblett Sr., his sons Ron Jr. and Rick, and Noblett's grandson, Tyler.
Rick Noblett said he was Trout's "golf and fishing buddy."
Asked how Trout hit a golf ball, Rick Noblett said: "Long. And straight. He puts balls places I've never seen people hit them."
Trout said this wasn't his first trip to Washington.
"I was here a couple of times on school trips," Trout said. "Not that long ago."
Trout began the game with a .307 average, with five home runs and 13 RBIs. Since the start of his first full season in 2012, Trout began the night ranked first in the major leagues in runs (252); second in batting average (.323), total bases (689), OBP (.414), OPS (.981), and stolen bases (84); and fifth in hits (395).
Harper entered the game with a .292 average, with one homer and five RBIs. He hasn't come close to matching Trout's career production.
Trout recently signed a six-year, $144.5 million contract extension that will kick in next season. He will make $1 million this season.
"He's the same guy," Scioscia said. "Even if he's not going really well, you don't see the frustration. He's very confident in his abilities."
Jeff Trout said his son has a great ability to "compartmentalize things."
"On the field, all he thinks about is baseball," Jeff Trout said. "Off the field, he's just Mikey."
Before the game, Mike Trout said he understood why he and Harper have been linked and why there was so much interest in this series.
"It's fun to be a part of it," Trout said. "You see two young guys playing in the same game in the same stadium, it's good for the fans."