Green Line sections were opened as indicated below.
Phase I Construction work on Reach 3 and 3A of Phase I of the Namma Metro began in 2009–10. The total cost of the project on this stretch was 2,100 crore. Work on the underground section commenced in May 2011.
Tunnel boring machines named
Kaveri, Krishna and
Godavari were used for tunnel boring work for the Green Line. The first trial run on the Green Line was conducted on 8 August 2013. Construction required 1.3 lakh tonnes of concrete, of steel bars, and of high tension wires weighing . A total of 395 piers, including station piers and portals, were constructed on the stretch. The tallest pier of the viaduct is a pier between
Mahakavi Kuvempu Road and
Srirampura stations, opposite Gayatri Devi Park. There 353 spans on the stretch, the longest being the curved span over the railway track off Srirampura. The total roofing area of the 10 stations on the stretch was . The first section of Green Line was opened to public on 1 March 2014. BMRCL Managing Director Pradeep Singh Kharola stated that about 25,000 passengers traveled on the line on the opening day. In the first month of operations, 7.62 lakh people at an average of 24,605 people daily used the Green Line, generating a revenue of . TBM
Godavari began drilling the underground section between Sampige Road and Majestic stations in April 2014.
Godavari broke down a few months later, and needed to have its cutter head replaced, due to contact with tough terrain including hard rock and boulders. The machine restarted work in September 2015 after importing the cutter head from Italy.
Godavari completed drilling and emerged on the Majestic station end of the tunnel on 19 April 2016. Meanwhile,
Kaveri and
Krishna drilled the underground section between National College and Nadaprabhu Kempegowda station. Construction of the underground section of Green Line required the use of 3,000 transit mixer loads of concrete. of cable had to be laid. Trial runs on the elevated section between National College and Yelachenahalli began on 23 November 2016. Trials were conducted between National College and Jayanagara initially at a speed of , and then along the entire elevated section between National College and Yelachenahalli at a speed of . Trial runs began in the tunneled section on 30 March 2017. Services at Sampige Road, Srirampura and Kuvempu Road stations were suspended between 13 and 22 March 2017 to allow authorities to conduct static and other tests and to link Sampige Road station with Nadaprabhu Kempegowda station. During the 10-day testing period, services operated only between Nagasandra and Rajajinagar stations. The BMTC introduced
rail replacement bus services from Rajajinagara to Hosahalli. Services between Sampige Road and Rajajinagara were suspended again for four days beginning 13 April 2017 to conduct trial runs on the underground section between Sampige Road and National College. Trial runs were completed on 16 May 2017.
Phase II Contract for construction of the 6.5 km Reach 4B from Yelachenahalli to Silk Institute was awarded to Nagarjuna Construction Co. The extension was estimated to cost . Civil work on the extension began in October 2016 and the extension was opened on 14 January 2021, making it the first section of Phase II to start commercial operations. In October 2016, BMRCL invited bids for the construction of viaduct and stations on the 3.031 km extension (Reach 3C) of the Green Line from Nagasandra to Madavara (previously named Bengaluru International Exhibition Centre). Reach 3C was awarded to Simplex Infrastructure Limited in late February 2017. The contract specified a cost of and a deadline for completion of 27 months. The start of construction on the extension was delayed by 4 months due to land acquisition issues concerning land near Jindal Aluminium Limited in Kirloskar Layout. The issues were resolved and construction began in June 2017. Trial runs were conducted in August 2024 and it was opened on 7 November 2024. After Phase II was completed, the line extended its stretch from Madavara in northwest to Silk Institute in the South. The length of the line increased to . Commercial operations on the Nagasandra-Madavara stretch started from November 7, 2024. There have been petitions to extend the line further south till the
Art of Living International Centre in the outskirts of Bengaluru. ==Stations==