On-loan Blackpool winger Ince took only 15 minutes to lift the ball over Ben Foster for the opening goal before Ledley - signed from Celtic in the January transfer window - rose to head Ince's corner into the net 12 minutes later.
The change had an immediate effect as Thievy beat Julian Speroni with a smart shot 30 seconds into the second period on his first start for his new club.
Speroni made an agile diving stop to deny Sinclair what looked like a certain equaliser. It was to prove a key moment as Ben Foster was deemed to have fouled Marouane Chamakh as he raced through the middle on 68 minutes.
Foster looked to have won the ball before tackling the man, but the referee Chris Foy decided otherwise as Chamakh converted the penalty to seal the three points for Palace with Speroni heading in the opposite direction.
Tony Pulis' side are up to 13th place in the table while West Brom are third bottom of the table in 18th place, but remain only three points behind Palace.
15' - INCE STRIKES: Ince breaks off Bolasie before lifting the loose ball over Foster after he went to ground. Brilliant finish from the new man. A 1-0 lead then for the home side.
27' - LEDLEY ADDS A SECOND: Ledley heads into the gaping net from the Ince corner. And that is a 2-0 lead for Palace. Brilliant start for the new men here.
46' - FRESH HOPE FOR WEST BROM: Thievy scores on his debut for the visiting side. Lovely pass from Anichebe. And that is a fine, fine finish. 2-1 now to Palace. Game back on.
64' - SPERONI HEROICS: Speroni comes up with a fine stop to deny Sinclair. Looked a certain goal after the ball broke to Sinclair from the Mulumbu shot. But a superb save low down to his left by Speroni.
68' - PENALTY TO PALACE: Against the run of play, but on the break as Marouane Chamakh is taken late by Foster. The West Brom keeper seemed to win the tackle and take the ball, but the referee said no.
69' - CHAMAKH SLOTS THE PENALTY: Marouane Chamakh sends the ball coolly to the left of Foster, who dived right. Fine finish. And that is a 3-1 lead for Palace. West Brom none too happy with that.
81' - ANICHEBE DRILLS A SHOT OVER THE BAR: Chance to set up a grandstand finish, but the former Everton forward can't come up with the finish as he drives the ball a few yards too high from 12 yards out.
Crystal Palace win three consecutive Premier League home matches for the first time since December 1992.
Tony Pulis has now recorded six Premier League victories against West Brom as manager, making them his equal-favourite opponents. He has also won six Premier League matches against Blackburn Rovers.
West Brom have lost their last two Premier League away matches. They last lost three away from home in succession between December 2012 and January 2013.
Tony Pulis has recorded five Premier League victories against West Brom as manager. He has only won more Premier League matches against Blackburn Rovers (6).
Crystal Palace have won their last two Premier League home matches. They last won three consecutive Premier League home matches in December 1992.
TALKING POINT: Are Palace on course to avoid the drop with their new signings? Has been said for some time now, but Tony Pulis knows his way around a football club. As we witnessed over many years at Stoke, he also knows a player when he sees one. With Ince and Ledley fitting snugly into the Palace routine and Glenn Murray back from a long-term injury, it is little wonder Palace look good to retain their Premier League status. Palace have taken 16 points from a possible 21 at Selhurst Park since Pulis replaced Ian Holloway in November which speaks for itself.
MAN OF THE MATCH
Tom Ince (Crystal Palace) Excellent introduction to life at Palace for the on-loan Blackpool winger. Could be a valuable addition as Palace look to safeguard their future in England's top flight.
Crystal Palace: Speroni 7, Ward 7, Dann 6, Delaney 6, Ledley 7, Puncheon 7, Dikgacoi 7, Jedinak 7, Bolasie 6, Ince 8, Chamakh 7..subs: Parr 6, Thomas 6, Murray 6
West Brom: Foster 7, Jones 6, McAuley 7, Dawson 6, Ridgewell 5, Yacob 5, Mulumbu 6, Gera 5, Morrison 6, Brunt 6, Anichebe 6..subs: Thievy 7, Berahino 6, Sinclair 6
- Sports & Recreation
- Premier League
- Tom Ince
- Julian Speroni
- Joe Ledley
- Scott Sinclair
- Marouane Chamakh
- West Bromwich Albion
- Ben Foster
- Tony Pulis