Inter Milan s players celebrate at the end of the Champions League quarter final first leg soccer match between Benfica and Inter Milan at Luz stadium in Lisbon, Tuesday, April 11, 2023. AP
The Italians, three time winners, took a commanding quarter-final first leg lead at the Estadio da Luz, inflicting Benfica's first defeat in the competition.
After an even first half, Barella headed home from Alessandro Bastoni's cross and substitute Romelu Lukaku netted the second from the penalty spot late on.
Roger Schmidt's Benfica, aiming to reach the semi-finals for the first time since 1990, were not able to put a glove on the visitors.
Despite Inter's poor form, they conjured a patient, professional display when they needed it most.
Having scored two goals in their previous five games across all competitions, they managed the same tally in Lisbon with clinical finishing.
Neither side was able to create clear chances in a tight opening period.
The closest Benfica came was Andre Onana blocking a Rafa Silva drive after Federico Dimarco accidentally headed the ball into his path in the box.
Inter Milan defender Francesco Acerbi hammered over from 30 yards at the other end.
The Italians had the opportunity to hit the hosts on the break after half an hour, but Lautaro Martinez played a poor pass which was blocked, with 37-year-old target man Edin Dzeko alone in space.
Alex Grimaldo smashed an effort wide from distance, with Benfica frustrated and unable to get striker Goncalo Ramos involved.
With Inter pressing high up the pitch, the Eagles struggled to Inter Milan broke the deadlock early in the second half when Barella headed Bastoni's looping cross back across goal and into the bottom corner.
Schmidt sent on David Neres for midfielder Florentino in search of the equaliser, but Inter doubled their lead with eight minutes remaining.
Joao Mario, one of Benfica's best players this season, handled Denzel Dumfries's cross, gifting his former side a penalty.
Lukaku drilled it beyond the reach of Greek goalkeeper Odysseas Vlachodimos, answering some criticism of his recent form.
Coach Simone Inzaghi had selected Dzeko ahead of Lukaku after the Belgian had missed gilt-edged chances in recent weeks, but he did not miss in a high-pressure moment.
Benfica might have pulled a goal back deep in stoppage time but Onana made a fine save to deny Ramos, who seemed poised to score.
The victory gives Inter a fine chance of setting up an all-Italian semi-final against Serie A leaders Napoli or city rivals AC Milan.
Inter host Benfica on Wednesday April 19 at the San Siro in the second leg.
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