"We were better in the passing game tonight," Kaepernick told reporters after passing for 235 yards.
"We made plays tonight. I think we can surpass (last season's level) if we keep working and getting our receivers healthy."
Last season's level included a trip to the Super Bowl, something San Francisco is hoping to duplicate.
Kaepernick, who has endured an up-and-down season, tossed a 19-yard touchdown to Anquan Boldin in the first quarter to get the visitors on the right track.
After Washington moved to within 10-6 at halftime, he struck twice more in the third on scoring throws to Boldin and Vernon Davis.
San Francisco has relied heavily on their running game lately but they only needed 31 rushing yards from lead back Frank Gore in the win.
Washington quarterback Robert Griffin passed for only 127 yards and an interception and could not get his team into the end zone.
The Redskins signal-caller spent the off-season recovering from a knee surgery and has failed to recapture the success of his magical rookie season.
Making matters worse, he has recently had his leadership called into question and dealt with team issues as the spiralling Redskins have now fallen to 3-8.
"I think we're all frustrated," Griffin said. "We're all tired of losing. (But) we're not quitters."
The Redskins managed 100 yards rushing, led by Alfred Morris' 52 yards.
Washington got two field goals from Kai Forbath in the second quarter but in the second half the home team failed to reach the red zone.
"We haven't gotten dominated like that since I've been here," said Redskins fourth-year coach Mike Shanahan, whose team managed just one first down and 30 yards in the second half.
(Writing by Jahmal Corner in Los Angeles, editing by Sudipto Ganguly/Amlan Chakraborty)
