The project is being funded by five major groups: MMRCL, Padeco, MMRDA, CREC, and JICA; the last of which provided a soft loan of ₹13,235 crore (US$1.5 billion)[12][13][14] The section of the line between Bandra Kurla Complex and Dharavi stations includes a 170-metre (560 ft) long twin-tunnel passing under the Mithi river.

[19][20] A 20 km (12.4 mi) metro line from Colaba to Bandra was announced in January 2004, as part of a master plan unveiled by the Mumbai Metropolitan Region Development Authority (MMRDA).

[21][28] Mumbai International Airport Limited (MIAL) agreed to bear the cost of constructing the three stations, which was expected to total ₹777 crore.

[37] In March 2019, the MMRC managing director Ashwini Bhide stated that the actual completion cost of the project is ₹30,000 crore (US$3.5 billion).

UPS Madan, Director, MMRC and Metropolitan Commissioner, MMRDA, explained, "The earlier logo was designed with an elevated Metro-3 corridor in mind as was planned originally.

[57][58] In March 2022, the Government of Maharashtra announced plans to extend Line 3 southbound from Cuffe Parade, adding one new station – Navy Nagar.

Sanjay Sethi, managing director of MMRC, stated, "The annual turnover requirement must have been set with the idea of attracting specific companies to the project.

According to Sanjay Sethi, managing director of MMRC, "We have finalised the list of companies eligible for bidding after getting an approval from the Japan International Cooperation Agency (JICA), which is providing more than 50 per cent of funds for the project.

[87][88] On 4 October 2019 after Bombay High Court dismissed the petitions rejecting application for stay on tree cutting at Aarey in the morning.

[94] The 120 year old, grade-I heritage structure that serves as the Western Railway Headquarter was reported to be under threat in December 2019 from the regular underground blasts at the Oval Maidan site of the Metro.

Verma's PIL concerned tree felling in Churchgate, Colaba and Cuffe Parade, and Jehangir challenged the use of public lands for construction of the line.

[102] On 12 April, the MMRDA filed its reply to petition declaring that the State Environment Impact Assessment Authority (SIEAA) had granted it permission to construct stations in Coastal Regulation Zone (CRZ) areas.

On 5 December 2016, the Union Environment Ministry issued a notification declaring the area up to 4 km from the boundary of the Sanjay Gandhi National Park to be an eco-sensitive zone.

On 5 January 2017, the NGT granted an exemption permitting the MMRC to construct a casting yard on a 3-hectare plot of land owned by the State Government in Aarey.

The forest department failed to provide the details at the next hearing, and on 17 February 2017, the NGT extended its stay on all construction activities up to 17 March 2017.

[119] Due to the issues surrounding the land at Aarey, Larsen & Toubro and Shanghai Tunnel Engineering Co., the consortium that was awarded the seventh package to carry out construction on the MIDC-Aarey Depot section of the line, exited the contract.

[121] A few weeks later, MMRC officials stated that the proposed depot could not be built at Mumbai University land in Kalina because the available area was too small.

[125] In March 2017, E. Sreedharan wrote to Chief Minister Fadnavis requesting him to ensure clearance for proposed metro depot at Aarey.

Sreedharan wrote, "Metro projects are environmentally most friendly and setting up a carshed in Aarey is not going to be a threat either to the government or to the eco system.

[130][131][132] On 16 April 2019, the Supreme Court rejected a petition filed the Aarey Conservation Group, a non-government organisation, seeking an alternative site to construct the depot.

[133] On 4 October 2019, Bombay High Court dismissed the petitions rejecting application for stay on tree cutting at Aarey in the morning.

[136] On 29 January 2020, the committee after studying suggested to lift the stay as they found no viable alternatives for car shed saying that MMRCL's arguments were valid.

[140] More than 100 Sub contractors and third parties have been used for various construction and relocation works including tunneling, boring, diversion of pipelines, realty consultancy and land acquisition.

[149] The section of the line between Bandra Kurla Complex and Dharavi stations includes a 170 metre long tunnel passing under the Mithi river.

Officials further added that if construction did not begin within one month, the project cost would escalate at the rate ₹4 crore (US$460,000) per day and would result in higher passenger fares.

As a result, contractors were unable to the enter the temple premises to map the location and conduct a building condition survey before beginning construction of the line.

Under pressure from the NITI Aayog, the Department of Economic Affairs, and the Ministry of Urban Development, JICA agreed to accept the Union Government's domestic manufacturing requirement for rolling stock for all JICA-funded metro systems in India.

[185] In September 2018, the MMRC awarded a EUR 315 million contract to French transportation major Alstom and its Indian subsidiary to supply 336 coaches for Metro 3.

Officials explained that providing luggage check-in would require additional dwell time at the Airport metro station, which would increase the overall headway of the line, and disrupt services for other passengers.

[191][192] In March 2017, the MMRC held a pre-bid meeting with all pre-qualified bidders for the "Design, Manufacture, Supply, Installation, Testing and Commissioning of Tunnel Ventilation & Environmental Control System.