Mumbai City

In early 2014, it was announced that the All India Football Federation, the national federation for Football in India, and IMG-Reliance would be accepting bids for ownership of eight of nine selected cities for the upcoming Indian Super League, an eight-team franchise league modeled along the lines of the Indian Premier League, the country's professional cricket league.

First season (2014) under Peter Reid

On 15 September 2014, the club signed Nicolas Anelka, a former French international who had been a free agent since his departure from West Bromwich Albion earlier in the year. Three days later, former Swedish international Freddie Ljungberg was signed as the team's first marquee player, returning from two years of retirement. Englishman Peter Reid was appointed as the team's first ever head coach.

Mumbai were the visitors in the first ever ISL match on 12 October 2014, at Atlético de Kolkata's Salt Lake Stadium. Without Anelka and Ljungberg, the side lost 3–0. On 18 October 2014, the club registered their first-ever ISL victory, defeating FC Pune City 5–0 at the DY Patil Stadium. In this match, Brazilian forward André Moritz registered the first ever hat-trick of the ISL. The team finished seventh out of eight in the table, and did not qualify for the playoffs.

Second season (2015) under Nicolas Anelka

In July 2015, Nicolas Anelka became player-manager, replacing Peter Reid. Frantz Bertin was appointed captain at the beginning of the season. The club then roped in then-India captain Sunil Chhetri for a domestic record-breaking deal of ₹1.2 crore, alongside signing the 2015 I-League Player of the Year Sony Norde of Haiti. Sunil Chhetri was the top scorer for the team, scoring seven goals including a hat-trick against NorthEast United FC. Mumbai only won four matches and lost six to finish in sixth position in the league table. Due to such results, Anelka opted not to renew his contract and left his position at the end of the season.

Alexandre Guimarães era (2016–2018)

After the first two seasons, Mumbai City's management made big changes by appointing Alexandre Guimarães, a former Costa Rica international, as the head coach for the 2016 ISL season. The club moved into their new home stadium, the Mumbai Football Arena, at Andheri. The club also signed 2010 FIFA World Cup Golden Ball winner Diego Forlán on a three-month deal, with the option to extend for another year as a marquee player for the season.

The arrival of the Uruguayan changed the dynamics of the struggling Mumbai team to title contenders. Forlán scored the first hat-trick of the Hero ISL 2016 season as The Islanders beat Kerala Blasters 5–0 at Mumbai Football Arena on 19 November 2016. It was also the first hat-trick of any marquee player in the history of the ISL. The team conceded the fewest goals (8) of all teams in the league, whilst Lucian Goian finished with the most tackles (67). Alexandre's team kept eight clean sheets in the group stage, making it a record across all three tournament editions. As a result, Mumbai City finished the 14 rounds at the top of the table, with six wins, five draws, and three losses. However, the club lost to ATK in the two-legged semi-finals.

In 2017, the ISL announced another auction in order to make way for new entrants Jamshedpur FC & Bengaluru FC, which led other clubs to start the squad rebuilding process once again. While Mumbai City missed their star performers, including the club's all-time top goalscorer Sunil Chhetri, the club managed to retain Alexandre Guimarães after he guided the club to their first-ever playoffs in three seasons. The club also managed to retain captain & goalkeeper Amrinder Singh for 12 million INR after he was awarded the best goalkeeper in the previous season, while keeping a record number of clean sheets for the club. They also retained the services of midfielder Sehnaj Singh who was instrumental in the club's success in the previous season. In the foreign department, they retained the defensive duo of Goian and Gerson Vieira, alongside Brazilian midfielder Léo Costa. They also retained Rakesh Oram, a player under the U-21 player quota.

However, the club's new signings did not perform at their best, as they finished the season in 7th position, failing to qualify for the playoffs, with the coach being criticized for overly defensive tactics. After the ISL season had concluded, Mumbai City FC also took part in the inaugural edition of the Super Cup. They kicked off proceedings smoothly by defeating Indian Arrows by a scoreline reading 2–1 in the qualifier round. However, they were defeated by East Bengal FC in the Round of 16. On 14 August 2018, The club stated that they and Alexandre Guimarães had parted company by mutual consent. This ended the Guimarães Era, with the Brazilian-born Costa Rican manager being with the Islanders since 2016.

Jorge Costa era (2018–2020)

After the announcement that Mumbai City FC had parted ways with Guimarães, the Islanders announced they had appointed former Portugal international Jorge Costa as the club's new head coach. The club also signed Indian Internationals Alen Deory and Subhasish Bose along with foreign players such as Modou Sougou, Rafael Bastos, Arnold Issoko and Paulo Machado.

The team started the season with a 2–0 loss at home to Jamshedpur FC, followed by a 1–1 draw to Kerala Blasters. The team then recorded a 2–0 win against FC Pune City, then lost 5–0 to rivals FC Goa. After that run of results, Jorge Costa made tactical changes, which led to the club's best unbeaten run in history at the time (9 games unbeaten). The team ended December with a 6–1 win against Kerala Blasters, with Modou Sougou scoring 4 of the team's six goals in the match, which was a record-breaking tally as Sougou became the first player in the league to score four goals in a single match. It was Mumbai's best-ever victory against any club. They also managed to break league leaders Bengaluru FC's unbeaten run at Mumbai Football Arena in January 2019.