After Robin van Persie's hat-trick against Olympiacos fired David Moyes' men into the UEFA Champions League quarter-finals on Wednesday, Rooney - stand-in captain due to Nemanja Vidic's suspension - gave everyone a timely reminder of his match-winning ability at Upton Park on Saturday.
Rooney was employed in a more advanced role due to Van Persie's absence with a knee injury, and the 28-year-old broke the deadlock with an ingenious looped half-volley from almost 50 yards in a goal reminiscent of David Beckham's memorable strike against Wimbledon in 1996.
Rooney had the chance to complete his hat-trick nine minutes after the break when he met Ashley Young's cross with a looped header, but United had to settle for the two-goal cushion.
Moyes was able to reflect on a rare successful week in a season of disappointments in his maiden campaign at Old Trafford, while Sam Allardyce's West Ham are not yet out of relegation trouble, though they remain six points clear of the drop zone in 14th.
The visitors could have moved ahead as early as the third minute when Marouane Fellaini's downward header was cleared just in front of goal by Andy Carroll.
But the away fans were soon celebrating Rooney's wonder-goal five minutes later.
That proved to be a double blow for the home side as, from the resulting counter-attack, Mark Noble cleared Young's cross straight at Rooney and he took advantage of the good fortune with a cushioned side-foot finish.
After settling into the half, Rooney missed the chance for his hat-trick by floating a header wide from Young's cross in the 54th minute.
Fellaini had a tentative claim for a penalty in the closing stages when he went to ground under Antonio Nocerino's challenge, but Mason was unmoved.
