The result came as another missed opportunity in the playoff race for Chennaiyin FC - they sit in eighth place, two points behind Bengaluru FC and three off the final playoff spot with a game in hand
Following the loss, FC Goa remained at fifth place on the standings. Up next for them is a clash at home against defending champions Hyderabad FC on January 5.
The Juggernauts kept more possession yet again but could not get the decisive touch as the Mariners kept their fourth clean sheet on the trot.
Smarting from a 0-3 reversal in Goa, ATK Mohun Bagan started on the front foot in what turned out to be a feisty first half with Boumous finding the winning strike in the 11th minute.
Mumbai City FC and ATK Mohun Bagan were involved in a high-octane 2-2 draw in the Indian Super League on Sunday
ATK Mohun Bagan once again grabbed the bragging right as it beat arch-rivals East Bengal 2-0 to register its fifth successive win in the Kolkata Derby in the Indian Super League on Saturday
Both East Bengal and Mohun Bagan will come into the derby on the back of a win and that will add some spice to the fixture
It was Ghanaian forward Kwame Karikari, who came in as a substitute in the second half and turned the match on its head, by first equalising in the 64th minute and then setting up India international Rahim Ali for the winner in the 83rd minute
Ashutosh Mehta accepted provisional suspension, which was optional in his case, on June 24.
An own goal by Sumeet Passi doomed East Bengal's fate as ATK Mohun Bagan returned to winning ways by thinnest of margins.
Earlier this month, FIFA had threatened to suspend the AIFF and strip off its right to host the women's U-17 World Cup in October
The Saltlake Stadium, which will host the summit clash on September 18, will play host to 10 games, including the opening derby between ATK Mohun Bagan and East Bengal, as well as all seven knockout games.
The Mariners head coach said the left-footed Florentin Pogba was on their wishlist and he was convinced only after learning about the club's vision
Paul Pogba's elder brother Florentin Pogba has signed a two-year contract with ATK Mohun Bagan
Hyderabad FC put one foot in what would be their maiden final appearance after scripting a come-from-behind 3-1 win over ATK Mohun Bagan in the first-leg of the Indian Super League second semifinal in Bambolim on Saturday.
Jamshedpur finished with 43 points from 20 games, winning 13 games. ATKMB ended their league engagements having 37 in their kitty from 20 matches.
Indian Super League: ATK Mohun Bagan rode on their talisman Roy Krishna's first-half strike to sail into the semifinals of the ISL for the second straight year, with a 1-0 victory against Chennaiyin FC on Thursday.
ATK Mohun Bagan took a big step towards booking a semi-final spot with a 2-0 win over Bengaluru FC in the Indian Super League (ISL) in Margao on Sunday.