A howler by Watford defender Samir allowed Rodrigo to double United's lead after Raphinha had put Leeds ahead with a stunning first-half strike.
Whites winger Jack Harrison, assisted by 20-year-old substitute Sam Greenwood, inflicted further misery on the Hornets with a third goal, ensuring Leeds took all three points back up the M1 with them.
The result took the Whites nine points clear of the Premier League drop zone, with 18th-placed Burnley set to take on fellow strugglers Norwich City on Sunday afternoon.
Graham Smyth, the YEP's chief football writer, hands out the scores.
The result took the Whites nine points clear of the Premier League drop zone, with 18th-placed Burnley set to take on fellow strugglers Norwich City on Sunday afternoon.