Jennings punished the hosts for dropping him on nought to repay the selectors' faith in him by scoring a brilliant hundred on a pitch that was spinning on the first day.
Moeen Ali also made 50 but Ravichandran Ashwin took four wickets and threatened to once again expose the England batting lineup but Ben Stokes and Jos Buttler at the end saw the visitors to decent score on a difficult pitch to bat on.
Both side made two changes as Cook choose to bat first
After an eight-day break, the fourth test got underway in Mumbai with Alistair Cook once again winning the toss and choosing to bat first in a must-win game for his side.
The visitors made two changes to their team from the third test with Jennings and Jake Ball replacing Haseeb Hameed and Gareth Batty in the team.
India also made two changes to their side with Bhuvneshwar Kumar and KL Rahul coming into the side to replace Mohammed Shami and Ajinka Rahane.
Cook and Jennings got the visitors off to a solid start
Cook and Jennings made their way to the crease to begin the day and they got the side off to the perfect start in the morning session as the pair saw off the early Indian threat by taking their partnership past the 50 mark.
Jennings showed how good he really is, as despite being dropped on nought, he made his way passed 50 as he looked to make the Indians pay for that drop.
Cook tried to join him near the end of the session by going past a half-century of his own but he didn't manage it as Ravindra Jadeja removed him for 46 as Parthiv Patel stumped the England captain as the partnership ended on 99.
Joe Root joined Jennings at the crease at the fall of the Cook wicket and both saw the team to lunch without losing any more wickets.
Therefore at lunch, England were on 117-1 with Jennings on 65 not out.
After lunch, Root and Jennings looked to settle in to try and take England to a big first innings score but Ashwin removed Root for 21.
Jennings showed his class with debut century
Moeen then joined Jennings at the crease and the pair took the attack to the Indian bowlers by taking their partnership passed the fifty mark.
Jennings was stuck for a while in the 90s but a lovely reverse sweep from the left-hander brought up his maiden century in his first test and he was one happy man with his performance.
Therefore at tea, England had once again had a brilliant session as they only lost the one wicket as the team ended the session on 196-2 with Jennings 103 not out and Ali on 15 not out.
After tea though the hosts started their fightback lead by the impressive Ashwin once more.
Ashwin lead hosts fightback but Stokes and Buttler saw the visitors to 288-5 at the end of the day
After some early hitting in the session from both the batsmen, Ashwin removed both within the space of three balls.
Firstly, Moeen fell for 50, two balls after reaching his half-century for a very poor shot. Jennings then fell for 112 when he was caught in the gully but he had done his job very well.
This meant India got two new batsmen at the crease without facing a ball as Jonny Bairstow and Stokes looked to build a partnership.
Just as he looked settled, though, Bairstow fell for 14 when he mistimed a sweep off Ashwin to leave England faltering on 249-5.
Stokes then was joined at the crease by Jos Buttler and the pair successfully saw the side to the close without losing any more wickets.
Therefore at the end of the day, the visitors finished on 228-5 with Stokes 15 not out and Buttler 18 not out.