Premier League: Fulham 3 West Bromwich Albion 0
Fulham and Bulgarian striker Dimitar Berbatov netted twice in the first half, while West Brom's woes were compounded when forward Peter Odemwingie was sent off for lashing out at Sascha Riether five minutes before the interval.
Sidwell wrapped up a deserved victory in the 89th minute, crashing a half-volley into an unguarded net.
Fulham started brightly, and almost took the lead when Berbatov tried to get on the end of Sascha Riether's cross, but Jonas Olsson was there to prevent him getting a touch.
James Morrison led West Brom's response, firing in an effort from the edge of the area, with Mark Schwarzer tipping over. Billy Jones then put in a dangerous ball across the six-yard box, but no-one was on hand for a tap in.
Fulham were pressing more as the first half wore on, and eventually found an opener just after the half-hour mark. Alex Kacaniklic had been finding lots of opportunities to run at the West Brom defence and this time he found Berbatov, who had time to take a touch and curl home a great effort into the top corner.
A little over five minutes later, Fulham's task was made a whole lot easier as Odemwingie inexplicably kicked out at Riether after losing the ball. It was a terrible decision from the striker, right in front of the home dugout, and he was swiftly shown the red card by referee Roger East.
As the first half entered stoppage time Kacaniklic rampaged down the left again and was brought down by Jones in the area for a clear penalty. Berbatov stepped up and made it look simple, sending Ben Foster the wrong way to double the lead at half-time.
Fulham exerted their dominance in the second half and brought the best out of Foster as a result.
The former Manchester United man made three superb stops in the space of a couple of minutes, with the third an outstanding reflex move to push the ball over the bar from Damien Duff's wickedly deflected shot.
The home side's dominance was clear, with attack after attack being launched on the visitors' goal, with only Foster preserving respectability in the scoreline.
Fulham's dominance was realised in the dying moments, when Sidwell crashed in a rebound after Hugo Rodallega's header hit the crossbar following good work from substitute Pajtim Kasami.