Cesc Fabregas gave Chelsea the lead in the first half with his first goal for the club in controversial circumstances.
However, Schalke refused to lie down and earned a battling point with a second half equaliser from Klaas-Jan Huntelaar to deny Chelsea a winning start to this season’s Champions League campaign.
The hosts started brightly and created their first opening on nine minutes when Schalke failed to clear a cross from Didier Drogba and the ball fell to Ramires inside the box, but the Brazilian got the ball stuck under his feet and failed to trouble Schalke keeper Ralf Fahrmann.
Chelsea broke the deadlock two minutes later in controversial circumstances through Fabregas. Fabregas appeared to foul Max Meyer in sliding in to try and win the ball back for Chelsea, but the referee failed to award a free-kick and Fabregas swapped passes with Eden Hazard to go clear on goal before slotting his shot past Fahrmann for his first goal for Chelsea.
Schalke were furious that the goal was allowed to stand with captain Huntelaar being booked for taking his protests too far.
Schalke fashioned their first chance of the game on 20 minutes when Sidney Sam cut in from the right and shot straight at Thibaut Courtois and a minute later Julian Draxler found space on the edge of the box only to drive his shot over the top.
Drogba had a sight of goal just past the half hour mark when Filipe Luis picked him out inside the box with an inviting cross, but the striker’s header lacked the power to trouble Fahrmann.
Chelsea really should have doubled their lead on 37 minutes when Branislav Ivanovic burst into the box from Ramires’ clever pass and pulled the ball back for Fabregas on the penalty spot and the goal at his mercy the midfielder lifted his shot over the crossbar.
Schalke were looking dangerous on the break and Kevin Prince-Boateng stung the palms of Courtois with a fierce strike from 30 yards on 39 minutes.
The visitors almost grabbed a leveller right on the stroke of half-time when Draxler set on on a fine solo run into the box and with the Chelsea defence standing off him he rolled his shot just wide of the far post.
Drogba wasted a great chance to double Chelsea’s lead four minutes into the second half when Willian got down the right and fired over a cross to Drogba six-yards out, but the big striker missed the ball altogether.
Chelsea continued to pour forward in search of a second goal and Ivanovic forced Fahrmann into a good save at his near post on 52 minutes after being found in the box by a clever pass from Fabregas.
Drogba really should have scored on the hour mark after Eden Hazard sent him racing clear on goal, but his first touch sent him wider than he wanted to and he dragged his shot across the face of goal.
Chelsea were made to pay for those missed opportunities two minutes later as Schalke caught with them a lightening counter attack as Huntelaar grabbed the equaliser.
Huntelaar robbed Fabregas of the ball midway inside his own half to set Draxler on a powerful run 50 yards downfield who picked out Huntelaar on the left and the Dutch striker cut in and drilled his shot low past Courtois.
Drogba’s miserable night continued on 66 minutes when Willian cut the ball back for the striker on the edge of the box, but the Ivory Coast ace drove his shot high over the crossbar.
Schalke continued to look dangerous on the break and the impressive Draxler fashioned a chance for himself on 70 minutes with some neat skill before driving in a shot which Courtois was forced to push away.
Jose Mourinho made a double change on 74 minutes from time with man of the moment Diego Costa and Loic Remy coming on for Drogba and Willian and two minutes later Remy almost scored when he saw his shot headed off the line by Roman Neustadter after Fahrmann flapped at a free-kick from Fabregas.
Chelsea poured forward in the final ten minutes in search of a winner and Hazard should have done better seven minutes from time when the ball dropped invitingly to him inside the box only to smash his volley over the crossbar.
A minute later Hazard had another sight of goal as Fabregas picked out his run into the box with a fine pass, but on the stretch the Belgian saw his shot turned round the post by Fahrmann.
John Terry went close to grabbing a winner in the final minute when he saw his header cleared off the line by Christian Fuchs, but Schalke held on for a draw.