Bayern Munich are the early leaders after a comfortable 2-0 win over Villarreal in Spain. Toni Kroos came of age in the Champions League, scoring the first, before Rafinha's neat nut meg allowed him to fire past Diego Lopez Rodriguez.
Manchester City and Napoli's Champions League bows ended with the points shared, as Aleksander Kolarov's free-kick cancelled out Edinson Cavani 69th minute strike.
Trabzonspor produced one of the biggest shocks in the history of the Champions League as they beat three-time European Cup winners as Ondrej Celustka's tight finish secured a memorable result at the San Siro.
French Champions Lille started their campaign in ideal fashion through Moussa Sow and Benoit Pedretti's goals either side of half-time, but Seydou Doumbia's late double, the second coming on the brink of full time after he exchanged passes with Alan Dzagoev, salvaged a point for CSKA Moscow.
Otelul Galati came within six minutes of securing their first Champions League point after Alexander Frei's penalty saved Basel's blushes in Switzerland.
Fabian Frei saw his 39th minute opener cancelled out by Marius Pena's delightful finish, but Adrian Salageanu's sending off, which led to Frei's penalty condemned the Romanian debutants to defeat. Benjamin Huggel was sent off late on, but it was too little, too late for Galati.
Benfica looked on course to secure just their second ever victory over Manchester United after Oscar Cardozo opened the scoring, but Ryan Giggs 20-yard effort meant the points were shared in Portugal.
Real Madrid required the guile of Angel Di Maria to unlock Dinamo Zagreb's defence, as the Argentine struck one of 23 efforts created by Jose Mourinho's side high into the net to confirm an opening game win, despite seeing Marcelo sent off for a second booking late on.
The other match between Ajax and Lyon saw one of only two draws on matchday one, with Hugo Lloris having to be at his best to keep out Christian Eriksen and Mirelem Sulejmani.
Valencia were unable to convert their dominance over Genk into goals as they drew a blank in Belgium. Adil Rami hit the bar with a stunning overhead kick, but it was the closest the La Liga side came.
Andre Villas-Boas' debut match in the Champions League saw his Chelsea side hit two second half goals to beat Bayer Leverkusen. Fernando Torres was at the centre of both goals, laying the ball off for David Luiz to curl home, before setting up fellow countryman Juan Mata in stoppage time.
Lucho Gonzalez's near post finish was enough to send Marseille top of Group F after against a limp Olympiakos in Pireas.
Meanwhile Arsenal came within two minutes of joining last season's Ligue 1 runners up at the top of the group, but Ivan Perisic's stunning volley cancelled out Robin Van Persie's first half goal.
Porto began their European season in disastrous circumstances as Hulk missed a fifth minute penalty against Shakhtar Donetsk, before Helton spilled Willian's long range effort into the path of Luis Adriano, who punished the Brazilian's error.
Just before the half hour mark Hulk made amends for his miss from the spot with a thunderous free-kick from 40-yards, before Kleber sealed the win after James Rodriguez's mazy run.
Apoel Nicosia scored twice in three second-half minutes to beat Zenit St Petersburg. Konstantin Zyryanov had earned the Russians the lead, but Bruno Alves' sending off helped turn the game on its head as Gustavo Manduca and Ailton completed the victory.
Barcelona's attempts to become the first side to win the European Cup in the Champions League era in successive seasons began with a draw with seven-time winners AC Milan.
Alexandre Pato scored the fifth fastest goal in Champions League history after 24-seconds at the Nou Camp, before Pedro and David Villa looked to have secured a win, before Thiago Silva's header in added on time stole a point.
Viktoria Plzen and BATE Borisov shared the points in Praha. Marek Bakos slide in to score on the brink of half-time for the hosts but Renan Bressan levelled it up with 20 minutes remaining.