The Argentine sensation, who was signed before the start of the season for a French record 42-million euro fee from Palermo, is expected to play after a three-week injury layoff that coincided with PSG's lack of creativity in midfield.
Pastore's presence was sorely missed when his team could only manage a goalless draw at Nice last Saturday with PSG dropping their first points since Carlo Ancelotti took over from Antoine Kombouare at the end of December.
The club from the capital also struggled in a 1-0 win at Dijon in a French Cup round of 16 tie on Wednesday as Jeremy Menez struggled to create chances for his team mates.
"We must be more efficient in attack," Ancelotti told reporters on Wednesday.
"What we showed would not be enough against Montpellier."
Ancelotti believes PSG needed to find ways to stretch defences if they were to score more goals.
"We need to use the whole width of the pitch because our opponents can too easily contain our three offensive players," he told a press conference earlier this week.
Pastore, whose silky touch and lightning-quick passes often put defenders on the back foot, should be back on Sunday as PSG, who have 50 points from 23 games, will be hoping to stretch their lead to four points.
"I think he [Pastore] will be ready for the Montpellier game," Ancelotti added.
Montpellier will once again rely on Olivier Giroud, the league's top scorer with 16 goals, who on Wednesday hinted he could stay next season if the side were to qualify for the Champions League.
"I want to play the Champions League and whether Montpellier are qualified for it or not will be a big factor in my decision," the France striker told a news conference.
Champions Lille, who have a game in hand and sit third on 39 points, travel to Lorient on Saturday looking to revive their title hopes after a dramatic 5-4 defeat to Girondins Bordeaux last weekend.
"We must quickly regain some balance," coach Rudi Garcia warned.
Bordeaux are six points behind Lille, occupiers of the final Champions League berth, after overcoming a disastrous start to the campaign and will host fourth-placed Olympique Lyon on Sunday.
Fifth-placed Olympique Marseille, unbeaten in their last 14 games in all competitions, entertain Valenciennes on Saturday.
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