The full-back rifled home from inside the penalty area in the 27th minute of Tuesday's semi-final tie at the Stade Pierre Mauroy and that proved enough to ensure a spot in the Stade de France showpiece.
Lille head coach Rene Girard aired his displeasure ahead of the contest that PSG had an extra day to recover for the match.
And his side certainly appeared the more sluggish in the opening exchanges as Edinson Cavani wasted two good chances before Maxwell's goal.
The tempo dropped somewhat in the second half with both teams struggling to create clear-cut chances.
Ultimately it was Laurent Blanc's men who emerged victorious and PSG - four-time winners of the competition - will now meet the winner of Wednesday's semi-final between Monaco and Bastia.
PSG dominated the opening exchanges and Cavani should have done better when he failed to make clean contact with Marquinhos' centre from the right, the Uruguayan's effort spooning out of play for a throw-in.
Cavani was at the heart of another promising attack in the 15th minute. Zlatan Ibrahimovic's quickly-taken free-kick fell to his fellow forward, who swept his effort straight at Vincent Enyeama.
The sustained pressure finally told shortly before the half-hour mark with Cavani once more playing an influential role.
The striker slipped in the area before recovering to collect Lucas Moura's probing throughball, and his sliding pass across the box was lashed home expertly by Maxwell into the roof of the net.
Lille appeared to be galvanised by falling behind and Idrissa Gueye flashed a shot wide of the left-hand post from the edge of the box.
PSG soaked up the pressure, though, and Lille's frustrations were evident when Florent Balmont was yellow-carded for a needless late shoulder charge on Marco Verratti, the latter too entering the book for taking revenge on the midfielder with a late challenge.
Enyeama had to be sharp to beat Cavani to the ball when Ibrahimovic's deflected cross from the right almost fell kindly into the path of his team-mate shortly after the break.
Referee Lionel Jaffredo then accidentally blocked an Ibrahimovic pass that appeared set to send Blaise Matuidi free.
In a similar fashion to the opening period, Lille looked composed on the ball until they reached the final third and PSG were largely comfortable.
Ibrahimovic thought he should have had a penalty with 20 minutes remaining when he went to ground under Marko Basa's challenge on the right of the box, but the defender appeared to win the ball.
Lille substitute Ryan Mendes - back from representing Cape Verde at the Africa Cup of Nations - was proving a threat and only a fine last-ditch tackle from Marquinhos prevented him from picking out a team-mate from the left of the area.
PSG safely saw out the closing stages to rack up a sixth straight win in all competitions and can now look ahead to a crucial Ligue 1 clash at leaders Lyon on Sunday, who they trail by two points.
