the English soccer season's traditional opener.
The Mexico striker stumbled as he met Antonio Valencia's cross, kicking the ball into his own face before it drifted into the net in the 76th minute.
"It's unbelievable to score and win this match," said Hernandez, a second-half substitute. "It's an unusual goal I scored."
Valencia had put United ahead after 41 minutes, racing to Wayne Rooney's low cross. Dimitar Berbatov scored in stoppage time to finish the victory. Chelsea's Salomon Kalou scored in the 83rd minute, getting the rebound after Edwin van der Sar stopped Daniel Sturridge's shot.
This is the third time in four years Manchester United has won the Community Shield. Chelsea won last year and went on to end United's three-year grip on the Premier League trophy.
United was limited to winning the League Cup last season, but resisted an overhaul. The only players to join the team were Hernandez and 20-year-old defender Chris Smalling from Fulham.
United opens league play Aug. 16 against Newcastle. Chelsea hosts West Bromwich Albion in the season opener Saturday.
"It's not been a good preseason, we have lost four games," Chelsea manager Carlo Ancelotti said. "We played too slow in the first half — it was not our best day. But this is normal, it can happen at the start of the season."
In the opening round of the Dutch league, FC Groningen held Ajax to a 2-2 draw and Feyenoord scored three goals in the second half to defeat FC Utrecht 3-1. In the Swedish league, Stefan Selakovic scored a hat trick to help IFK Goteborg rout Hacken 5-1.