[8] On 31 May, the Islanders announced the departures of Hardik Bhatt (on loan), Gursimrat Singh Gill and Raynier Fernandes from the club as their contracts ended on the same day.

[9][10][11] On 1 June, the Islanders welcomed back Spaniard Juanma Cruz as their new first-team goalkeeping coach till the end of the 2023–24 season.

[18] On 19 June, the Islanders announced the signing of Indian left-back Akash Mishra from Hyderabad FC for an undisclosed transfer fee till 2028 on a five-year deal.

[19] On 24 June, the Islanders announced the permanent signing of Vinit Rai from Odisha FC following his loan spell till the end of the 2023–24 season.

[24] On 10 July, the Islanders announced the departure Indian left-back Vignesh Dakshinamurthy to Hyderabad FC for an undisclosed fee after spending five years at the club.

[29] On 17 July, the Islanders were drawn in Group B for the 132nd edition of the Durand Cup, alongside Indian Navy, Jamshedpur FC and Mohammedan SC.

[30] On 22 July, the Islanders announced the signing of Indian attacking midfielder Jayesh Rane on a season-long loan from Bengaluru FC.

[32] On 30 July, the Islanders played their first tour pre-season friendly match against Thai League 1 side PT Prachuap, which they won 3–0.

[34] On 5 August, the Islanders played their first group stage match in the Durand Cup against I-League side Mohammedan SC, which ended in a 1–3 win.

[36] On 14 August, the Islanders announced the departure of striker Mustafa Shaikh to Sporting Club Bengaluru on a season-long loan deal.

[37] On 14 August, the Islanders announced the departure of Indian midfielder, Mohammed Asif Khan, to Inter Kashi for an undisclosed fee after spending five years at the club from the age of 14.

[28] On 16 July 2023, Mumbai City announced that they would travel to Thailand on a pre-season tour in preparation for the Durand Cup campaign in August.

[30][32] Win Draw Loss As a result of finishing top of the group, Mumbai City advanced directly to the quarter-finals.