Porto was yet to concede this season, but Talisca, Cenk Tosun, and Ryan Babel all scored for Besiktas at Estadio do Dragao for a resounding win.
Besiktas managed to break through FC Porto's defence to open its Champions League campaign with a 3-1 win on Wednesday.
Porto was yet to concede this season, but Talisca, Cenk Tosun, and Ryan Babel all scored for the visitors at Estadio do Dragao.
After Talisca opened the scoring, Porto equalized thanks to an own goal by Besiktas defender Dusko Tosic.
Tosun gave the Turkish side the lead again before halftime, and Babel sealed the victory in the second half.
"It was a great game from us, defensively as well as in attack," Talisca said.
"We did exactly what our coach asked of us and everything worked out well. We had a very good first half, while Porto dominated us somewhat in the second but we knew how to stand up to that."
Porto has won only two of its last eight home matches in European competitions.
It was coming off five straight wins to start the season in Portugal, all without conceding.
Porto was without Vincent Aboubakar and Maxi Pereira because of suspensions. Aboubakar played on loan with Besiktas last season.
"We had enough chances to have ended with a different result," Porto coach Sergio Conceicao said.
Ronaldo back in style
In the day's other fixtures, Cristiano Ronaldo grabbed a brace on his return from suspension for Real Madrid, as Tottenham Hotspur ended their Wembley jinx and Liverpool were held on their Champions League comeback.
Real have sorely missed their Portuguese superstar as he serves a five-match domestic ban for pushing a referee.
But he wasted no time in making his towering presence felt against APOEL Nicosia, scoring after just 12 minutes from Gareth Bale's low cross, and then doubling his tally from the penalty spot before Sergio Ramos's overhead kick rounded off the cosy 3-0 win.
Ronaldo has now struck 12 times in his last six Champions League games.
The titleholders top Group H with Tottenham, who ended their woeful Wembley run with an impressive Harry Kane-inspired 3-1 win over Borussia Dortmund.
At Anfield, Roberto Firmino's first-half penalty miss proved costly for Liverpool as Joaquin Correa scored a dramatic equaliser to grab Sevilla a 2-2 draw.
Liverpool and Sevilla were joined on one point in Group E by Spartak Moscow and Maribor, who drew 1-1 in Slovenia.
English giants Manchester City ran out the biggest winners of the night with a 4-0 rout of Feyenoord in Rotterdam courtesy of goals from Sergio Aguero, Gabriel Jesus and John Stones' double.
Shakhtar Donetsk beat Napoli 2-1 to share the summit in Group F while French champions Monaco were held 1-1 at competition newcomers RB Leipzig in Germany.