Match ends, Real Madrid 1, Espanyol 0.
Real Madrid moved top of La Liga after Marco Asensio's VAR-awarded strike proved enough to beat Espanyol.
Asensio drilled in a low shot just before the break when Luka Modric's effort deflected into his path, with the goal given after a lengthy review.
Borja Iglesias hit the crossbar for the spirited visitors with a deft chip.
Former Real keeper Diego Lopez made a fine save to deny Sergio Ramos late on in an otherwise stilted performance by the hosts at the Bernabeu.
Victory takes Julen Lopetegui's side above rivals Barcelona, who can retake the top spot with a draw or victory against Girona on Sunday.
Espanyol drop to sixth following Atletico Madrid's 2-0 win over Getafe earlier on Saturday.
Real made sure of victory with a functional rather than fluent performance, maintaining their unbeaten league start under new boss Lopetegui.
Isco and Asensio once again showed how vital they will be to the new era at the Bernabeu after the departure of talisman Cristiano Ronaldo and three-time Champions League-winning manager Zinedine Zidane over the summer, the Spain pair central to most of their side's best moves.
Asensio was unmarked when Modric's blocked strike fell to him and clinically found the far bottom corner as Espanyol appealed for offside.
Referee Antonio Miguel Mateu Lahoz consulted VAR and after a long delay awarded the goal, with replays showing Asesnio was clearly onside, as the midfielder appeared to joke about the wait with his celebration, pointing to his wrist.
Isco then created Real's best chance in the latter stages, curving an immaculate cross with the outside of his right foot, only for Lopez to tip the onrushing Ramos' header over the bar.
The lack of fluency could also be down to the hosts making five changes from the side that beat Roma in the Champions League on Wednesday, with Gareth Bale an unused substitute.
While right-back Alvaro Odriozola made a largely assured debut, Real's defence as a whole was suspect at times but Espanyol failed to take advantage.
Pablo Piatti shot just wide after Real were slow to react to a sweeping Espanyol counter, before former Chelsea keeper Thibaut Courtois saved from Hernan Perez.
After the interval, Ramos was caught dallying in possession on the edge of his own area, with Iglesias robbing him off the ball and beating Courtois with an exquisite lob only to see it ricochet back off the bar.
Despite that warning, Ramos continued to streak forward at will, with Casemiro forced to race back and cover on several occasions. The experienced Spaniard could have cost his side the win, had the visitors been more clinical with their final ball.
Match ends, Real Madrid 1, Espanyol 0.
Second Half ends, Real Madrid 1, Espanyol 0.
Luka Modric (Real Madrid) wins a free kick in the attacking half.
Foul by Víctor Sánchez (Espanyol).
Foul by Marcos Llorente (Real Madrid).
Javi López (Espanyol) wins a free kick in the defensive half.
Hand ball by Esteban Granero (Espanyol).
Casemiro (Real Madrid) wins a free kick in the defensive half.
Foul by Dídac Vilá (Espanyol).
Attempt saved. Marcos Llorente (Real Madrid) right footed shot from the right side of the box is saved in the top centre of the goal. Assisted by Mariano.
Corner, Espanyol. Conceded by Sergio Ramos.
Attempt blocked. Leo Baptistao (Espanyol) right footed shot from the left side of the box is blocked. Assisted by Borja Iglesias.
Attempt missed. Marco Asensio (Real Madrid) left footed shot from outside the box is high and wide to the left. Assisted by Mariano.
Luka Modric (Real Madrid) wins a free kick in the defensive half.
Foul by Leo Baptistao (Espanyol).
Attempt missed. Javi López (Espanyol) right footed shot from the centre of the box misses to the left. Assisted by Esteban Granero following a corner.
Substitution, Real Madrid. Marcos Llorente replaces Isco.
Corner, Espanyol. Conceded by Raphael Varane.
Attempt blocked. Esteban Granero (Espanyol) right footed shot from outside the box is blocked.
Casemiro (Real Madrid) is shown the yellow card for a bad foul.
Foul by Casemiro (Real Madrid).
Borja Iglesias (Espanyol) wins a free kick in the attacking half.
Attempt saved. Lucas Vázquez (Real Madrid) left footed shot from the centre of the box is saved in the centre of the goal. Assisted by Luka Modric.
Corner, Real Madrid. Conceded by Diego López.
Attempt saved. Sergio Ramos (Real Madrid) header from the centre of the box is saved in the top centre of the goal. Assisted by Isco with a cross.
Substitution, Espanyol. Sergio García replaces Hernán Pérez.
Corner, Real Madrid. Conceded by Marc Roca.
Attempt blocked. Mariano (Real Madrid) left footed shot from the centre of the box is blocked.
Attempt saved. Marc Roca (Espanyol) left footed shot from outside the box is saved in the bottom right corner.
Borja Iglesias (Espanyol) hits the bar with a right footed shot from outside the box.
Attempt saved. Borja Iglesias (Espanyol) left footed shot from outside the box is saved in the bottom right corner. Assisted by Leo Baptistao.
Corner, Espanyol. Conceded by Casemiro.
Attempt blocked. Borja Iglesias (Espanyol) right footed shot from outside the box is blocked. Assisted by Diego López.
Substitution, Real Madrid. Lucas Vázquez replaces Dani Ceballos.
Offside, Real Madrid. Marco Asensio tries a through ball, but Luka Modric is caught offside.
Attempt missed. Marco Asensio (Real Madrid) left footed shot from outside the box misses to the left following a corner.
Corner, Real Madrid. Conceded by Mario Hermoso.
Attempt blocked. Luka Modric (Real Madrid) left footed shot from outside the box is blocked. Assisted by Isco.
Substitution, Real Madrid. Mariano replaces Karim Benzema.
Attempt missed. Casemiro (Real Madrid) right footed shot from outside the box misses to the right. Assisted by Dani Ceballos.