Defensemen Joe Reekie and Ken Klee had even-strength goals for the Caps, and forward Martin Gendron scored on a power play.
The Flyers had nearly all of their top guns in the lineup, while the Caps inserted young players among their veterans.
"It's the kind of game you always expect between our two teams," said Philadelphia coach Terry Murray. "We're in the same division and we're both very competitive."
Caps coach Jim Schoenfeld said his team played better after the first period, when it was on the defensive. In fact, Washington had just eight shots in the first two periods, scoring on three of them against Ron Hextall.
Jim Carey and Olie Kolzig split time in goal for Washington, Carey allowing three goals and Kolzig giving up LeClair's game-winner.
The Caps will leave today for a four-game road trip. Washington plays at San Jose tomorrow and at Anaheim on Wednesday, then meets the Ottawa Senators in Sudbury on Friday and in Ottawa on Saturday.