Match ends, Crystal Palace 1, Middlesbrough 0.
Patrick van Aanholt scored the winner for Crystal Palace, as they moved out of the Premier League relegation zone with victory over struggling Middlesbrough.
Palace had the better of the first half and deservedly took the lead through the Dutchman's low drive from the edge of the box - his first goal since joining the club in the January transfer window.
Chasing the game in the second half, Boro's Cristhian Stuani struck an effort straight at Wayne Hennessey from inside the area, and Fabio sent a shot over the crossbar late on.
The Teessiders have now failed to win in their past nine league games and are 16th in the table, one point above the relegation zone and level on points with their opponents.
The victory for Palace also drops champions Leicester into the bottom three.
Sakho aids Palace survival hopes
Sam Allardyce had won just once in eight games since taking over as Palace boss in December and questions were being asked about whether he had returned to football too soon after his embarrassing departure from the England job, or been affected by that experience.
Allardyce has never been relegated from the top flight and told Football Focus before the game that the problems at Selhurst Park "were a lot deeper than he had expected".
But the Eagles collected a priceless win - their third at home this season - to boost their own survival hopes, while pushing managerless Leicester deeper into trouble.
Goalkeeper Hennessey made four comfortable saves as he helped his side to just their second clean sheet of the campaign, but debutant Mamadou Sakho was a towering presence at the back.
The Frenchman, signed on loan from Liverpool in January, was making his first start of the season and in an assured performance, he won the ball back 11 times and made six clearances, which was more than any team-mate.
Boro firing blanks
Aitor Karanka's side have won just four games all season, fewer than any other side in the division.
Their biggest problem is scoring goals, having found the net a mere 19 times in 26 games on their return to the Premier League, and this was their third consecutive league game without a goal.
Uruguayan Stuani, who has scored four of those 19, had their best opportunity to claim a point, but his angled shot from inside the area caused Hennessey no problems.
Striker Rudy Gestede was signed from Aston Villa in the transfer window to boost their front line, but the £6m acquisition failed to make an impact after appearing as a half-time substitute.
Having lost against a relegation rival, Boro will be hoping to pick up maximum points against fellow strugglers Swansea, Hull and Bournemouth, who they face in their remaining 13 games.
Man of the match - Mamadou Sakho (Crystal Palace)
'Our approach was not the best'
Crystal Palace manager Sam Allardyce: "Selhurst Park was rocking today. It felt like they really enjoyed the commitment from the players and really got behind us.
"For me it was all about the quality in the first half we continued to pepper Middlesbrough's box with crosses and shots and it came to Patrick van Aanholt and he scored with his weaker foot.
"We need that sort of quality if we are going to stay up and he has proved himself with four goals this season now - three for Sunderland, one for us."
Crystal Palace full-back Patrick Van Aanholt: "I lost my granddad last week. I am very pleased to get the goal for him. Obviously I am very sad to lose him but I thank him a lot."
Middlesbrough manager Aitor Karanka: "It difficult to lose but we have to keep going.
"This is not the first time I'm living this situation but the only thing I know is to keep working.
"The way we approached the game wasn't the best. I didn't need to say how important the game was to win - I think everyone knew."
Ex-England striker Alan Shearer: "It was a performance that deserved three points. Other than the 10 minutes after half-time I thought they were the much better team throughout.
"They understood what each other's roles were, how they were going to play the game. They just did not hesitate at all to get balls into the box. They knew, I think, that they had to do that.
"That was their first thought - can we hit the big man, even if there's no bodies around him? Second half, that didn't change either. They thoroughly deserved the three points today and it was three massive points for them.
"We say the same thing every week about Boro - 19 goals, 26 games, they haven't won since mid-December, not won in nine. They're in a slump and they're in big trouble, I think."
Capital punishment for Boro - the stats
- Palace ended their run of five home league defeats in a row, the longest such run by any team in the Premier League this season.
- Middlesbrough remain on the current longest winless run in the Premier League, failing to win any of their past nine games, drawing four and losing five.
- Sam Allardyce enjoyed his first win in his past 10 Premier League games against Middlesbrough (drawn six, lost three).
- Aitor Karanka's Boro side have scored a league-low 19 goals, while their top-flight games have produced a total of 47 goals, 12 fewer than any other team in the competition this season.
- Middlesbrough have failed to win on any of their past 13 Premier League visits to London (drawn four, lost nine), last winning in the capital at Fulham 2-1 in August 2007.
- Patrick van Aanholt is the first player this season to score for two clubs in the Premier League (excluding own-goals), also netting for Sunderland.
- Van Aanholt has scored eight goals in the Premier League since the start of last season - a joint-high for a defender (excluding penalties), with team-mate Scott Dann also netting eight.
- Yohan Cabaye registered a Premier League assist for the first time in his past 48 Premier League appearances (since 3 October 2015 against West Brom).
Crystal Palace travel to West Brom next Saturday (kick-off 15:00 GMT), while Middlesbrough go to Stoke at the same time.
- 2WardBooked at 83mins
- 3van AanholtSubstituted forSchluppat 87'minutes
- 7CabayeBooked at 30minsSubstituted forMcArthurat 63'minutesBooked at 76mins
- 11ZahaSubstituted forDannat 88'minutes
- 2da SilvaBooked at 75mins
- 14de Roon
- 34ForshawSubstituted forGuédiouraat 61'minutes
- 10NegredoSubstituted forGestedeat 45'minutes
- 18StuaniSubstituted forTraoréat 79'minutes
- Robert Madley
- Shots on Target
Second Half ends, Crystal Palace 1, Middlesbrough 0.
Foul by Daniel Ayala (Middlesbrough).
James McArthur (Crystal Palace) wins a free kick on the left wing.
Dangerous play by Gastón Ramírez (Middlesbrough).
Wayne Hennessey (Crystal Palace) wins a free kick in the defensive half.
Attempt missed. Andros Townsend (Crystal Palace) right footed shot from the right side of the box is close, but misses the top right corner. Assisted by Christian Benteke following a fast break.
Foul by Daniel Ayala (Middlesbrough).
Christian Benteke (Crystal Palace) wins a free kick in the defensive half.
Attempt missed. Adlène Guédioura (Middlesbrough) right footed shot from outside the box misses to the right. Assisted by Gastón Ramírez.
Substitution, Crystal Palace. Scott Dann replaces Wilfried Zaha.
Substitution, Crystal Palace. Jeffrey Schlupp replaces Patrick van Aanholt because of an injury.
Attempt missed. Fabio (Middlesbrough) right footed shot from the right side of the box is high and wide to the left. Assisted by Rudy Gestede with a headed pass.
Delay over. They are ready to continue.
Delay in match Patrick van Aanholt (Crystal Palace) because of an injury.
Attempt missed. Ben Gibson (Middlesbrough) header from the left side of the six yard box misses to the left. Assisted by Fabio with a cross.
Joel Ward (Crystal Palace) is shown the yellow card for a bad foul.
Rudy Gestede (Middlesbrough) wins a free kick in the defensive half.
Foul by Joel Ward (Crystal Palace).
Corner, Crystal Palace. Conceded by Daniel Ayala.