The Stade Velodrome had been the venue for Liverpool's European salvation last season, and Gerrard made sure it was a welcome return to the south of France.
Marseille had taken the lead through their skipper Lorik Cana, but Gerrard - already Liverpool's record scorer in Europe - grabbed a fine equaliser with an outstanding 25-yard curler.
Then six minutes later he cracked home a twice-taken penalty to give Liverpool something to hang on to.
And they needed to fight hard as the French side battled bravely in the second period, but Liverpool clinched their victory with a defiant rearguard action.
The Reds included both Gerrard and Fernando Torres in their starting line-up for the opening group D clash.
Both key players have been recovering from injury and their inclusion was a major boost for the Anfield club.
Andreas Dossena came into the side in place of calf-injury victim Fabio Arbeloa, while Lucas took over in midfield from Xabi Alonso.
Marseille, who won 1-0 in the Champions League last term at Anfield before losing the return 4-0, included Hatem Ben Arfa, their £10m signing from Lyon, who had recovered from an ankle problem.
Skipper Cana also returned, having been rested at the weekend in the draw at Bordeaux.
Liverpool had opted for caution with Robbie Keane and Albert Riera both on the bench. Gerrard was being used in the attacking midfield role that worked to such good effect last season, and several times early on Liverpool could have scored.
After just seven minutes, Steve Mandanda tipped over a Lucas header and soon afterwards Dirk Kuyt's pass set-up Ryan Babel.
The Dutchman created the space with his first touch but blasted a good opening high over. Then Gerrard forced Mandanda into a diving save before Torres saw a header clear the far angle.
Marseille had chances of their own. Mamadou Niang was clear on the left but wasted the opportunity, shooting high over. Martin Skrtel was booked for a late tackle on Niang after 20 minutes as the game became surprisingly open.
But after 23 minutes the French side were ahead when they caught Liverpool square and punished them with a fine goal.
Rarely are Liverpool exposed straight through the middle, but when Benoit Cheyrou's first-time ball sent Cana clear, his quality side-footed finish sent the Velodrome fans wild.
Liverpool's response was emphatic.
Two minutes later Torres won possession on the halfway line and presented Kuyt with a pass on the right that was instantly played into Gerrard's path.
The Liverpool skipper struck a first-time, curling effort from 25-yards that soared over Mandanda into the far corner for the equaliser.
And after 31 minutes Liverpool were ahead. Babel's sharp turn in the box ended with Ronald Zubar's trip and a penalty. Zubar was booked before Gerrard struck the ball past Mandanda off the post.
But Austrian referee Konrad Plautz ordered a re-take because Kuyt had encroached into the box. Gerrard kept his nerve and clinically netted a second time to put Liverpool ahead.
The double strike extended Gerrard's European goals record for the club. Last season, in the Anfield side's 4-0 win in Marseille, Gerrard's goal that night broke Michael Owen's benchmark of 23.
He extended that tally later in the competition to 25, and two more here in the opening half for the captain stretched his tally to 27, and 99 for the club in all competitions.
Marseille were stunned and soon sent on Mathieu Valbuena for the injured Modeste M'Bami after 41 minutes.
Ben Arfa lasted until the 56th minute before his ankle problem forced him off, Karim Ziani taking over.
The game was still very open. Babel almost forced the ball around Mandanda at one end, while Liverpool were making too many defensive errors at the other for Benitez to rest easy.
Marseille could easily have been level when Vitorino Hilton met a corner with a fierce downward header that Jose Reina managed to hold on to.
Liverpool sent on Riera after 64 minutes for Torres, who had looked short of pace after his spell out, before Ziani struck a 12-yarder over the bar as Marseille searched for parity.
The Reds then withdrew Gerrard after 68 minutes, sending on Yossi Benayoun with Babel now the lone striker.
Liverpool had got the most possible out of their recently-injured stars, and it was now left to their colleagues to withstand a mounting Marseille onslaught.
Ziani fired over again before Mamadou Samassa replaced Bakari Kone.
Babel saw a golden chance to finish the contest go to waste after 74 minutes when Riera and Benayoun set him up close in, only for Mandanda to save the point-blank effort.
The youngster then struck the post after 78 minutes as he surged through on the left. But still Marseille came forward searching for the equaliser as Liverpool sought to punish them on the break.
With five minutes left, Kuyt was replaced by Keane, fresh legs to the cause as Liverpool continued to hang on.
Niang saw a diving header go wide from a right-wing cross, Marseille still fighting for an equaliser.
Reina saved superbly in injury-time from Niang and Liverpool had their victory.
