Copa del Rey: Atletico Madrid 2 Real Madrid 0
Fans' favourite Torres was the centre of attention at Vicente Calderon after rejoining the Spanish champions from Milan last week, having agreed a loan deal until the end of next season.
However, it was Raul Garcia from the penalty spot and Jose Gimenez who made sure of this first-leg triumph.
Raul Garcia's 58th-minute opener came after he had been hauled to the floor by Real captain Sergio Ramos in the area, before Gimenez headed the second 14 minutes from time.
The returning Torres scored 91 goals in 244 games for Atleti after making his debut at the age of 17, prior to moving to Liverpool back in 2007.
The 30-year-old struggled for form after leaving the Merseyside club to join Chelsea, but he was greeted by more than 45,000 fans when he was unveiled at the Calderon on Sunday.
Torres was given a hero's reception again here, although he failed to have too much of an impact during his hour on the pitch.
Nevertheless, he will no doubt be satisfied with a victory over fierce local rivals Real in his first game back.
Torres' inclusion gave Atleti a welcome boost, and it was soon followed by another when Carlo Ancelotti opted to leave Cristiano Ronaldo on the bench as Real's fringe players such as Keylor Navas, Raphael Varane and Sami Khedira were given a chance to shine.
Ramos threatened to spoil international colleague Torres' homecoming with less than a minute on the clock, but a powerful fisted save from Jan Oblak kept out the defender's header from a corner.
Torres was caught offside at the other end as he looked to grab a memorable goal, before Gareth Bale looked to have put Real in front with a header in the 13th minute, only for the assistant referee to correctly flag for offside.
Atleti went on the counter-attack after Bale's effort had been ruled out, but Antoine Griezmann had a strike tipped wide by Navas, before drawing an excellent last-ditch tackle from Varane.
A clash between Raul Garcia and Khedira went unnoticed by the officials – the German hitting the deck after an apparent push in the face – before the Atleti man saw an effort blocked in the box by Marcelo.
Karim Benzema forced Oblak into a routine save from 20 yards six minutes from the interval, but clear-cut chances were few and far between, despite the fast pace of the opening period.
As they had done in the first half, Real started the second on the front foot, and Bale guided the ball just wide of the left-hand upright after receiving a superb pass over the top from Marcelo.
Ramos then hauled Raul Garcia to the ground in the 58th minute to give the hosts the chance to break the deadlock from the penalty spot, although there was some suggestion of shirt pulling from the Atleti man.
The midfielder, who arguably should not have been on the pitch following his clash with Khedira, stepped up to take the spot-kick himself, and expertly dispatched the ball into the bottom-right corner.
Torres left the field to be replaced by Koke after Atleti had taken the lead, while Ancelotti threw on Ronaldo in a bid to restore parity.
The Portuguese's introduction had little impact, though, and Gimenez headed Atleti's second from a corner in the 76th minute.
That was enough to send the hosts into the second leg with a comfortable two-goal advantage, as Real were beaten again just a few days after seeing their record-breaking winning streak ended by Valencia.