The home side opened the scoring after 19 minutes when Neymar, who was taking part in his first El Clasico, slotted a low effort into the bottom corner.
Real Madrid had most of the opportunities in the second period, but a strike from Sanchez after 78 minutes secured all the points for Barcelona, despite Jese Rodriguez registering late on for the away side.
Here, Sports Mole dissects the 90 minutes of action between the two Spanish rivals.
On target: 5
On target: 6
Was the result fair?
In truth, neither side did enough to pick up all three points this evening. As expected, Barcelona dominated possession in the early stages of the first period, but Madrid certainly had their moments as the half advanced. The away side attempted to force the issue on the counter attack in the second half, but could not create too much of note. If one side had to win it, then Barcelona might argue that they just about deserved all the points on their home patch.
Barcelona might have picked up all three points in their most important fixture of the season, but they are still not quite at their best, which is a scary thought for the rest of the division and indeed rest of Europe. Lionel Messi had a very quiet match, but Neymar stepped up to the mark with an impressive first-half display. The Catalan outfit were under pressure for large periods of the second half, but they managed to soak up the danger before scoring a second.
Something is not quite right with Madrid at the moment. It was certainly a surprise that Carlo Ancelotti decided to line up with Sergio Ramos in midfield. Gareth Bale, meanwhile, started through the middle, and the Welshman was unable to really threaten during a disappointing evening. On another night, they might have taken a point from the Camp Nou, but they were not as threatening on the counter as they have been in previous seasons. Too many of their big players were under-par this evening.
Sports Mole's man of the match
Neymar: Granted, the Brazilian did not feature too heavily in the second period, but he was just sensational in the first. The former Santos attacker opened the scoring with a curling effort inside 19 minutes, while he caused the away side all sorts of problems with his pace and movement in the final third. One goal in one Clasico for the youngster.
Biggest gaffe of the match
With his side leading in the second period, Javier Mascherano decided to barge Cristiano Ronaldo to the ground inside the penalty box. The decision was not given, but the Argentine might have cost his side with a moment of madness. Ronaldo certainly felt that a penalty should have been awarded, with the Portuguese later gaining a yellow card for arguing the decision.
The man in the middle this evening was Alberto Undiano. El Clasico is one of the hardest matches to referee in world football, but the Spaniard, on the whole, had a respectable evening. He was forced to deal with a number of challenges in the first period, but managed to calm proceedings. The major incident in the second period saw Mascherano barge Ronaldo to the floor inside the box, but the referee was not interested - a decision that angered those involved with Madrid.
Barcelona: The Catalan outfit are next in league action on Tuesday when they make the trip to a struggling Celta Vigo side.
Madrid: Ancelotti's side will attempt to return to winning ways when they welcome Sevilla to the Spanish capital on Wednesday.