It is fully automated and driverless, the first system of its kind in Greece, and is operated by Thessaloniki Metro Automatic (THEMA), a Franco-Italian consortium.

[6][7] Although Thessaloniki has grown considerably since Hébrard's original design, Line 1 is almost identical to his plan and runs from his proposed new railway station to the suburb of Nea Elvetia.

The Thessaloniki chapter of the Technical Chamber of Greece started considering a metro system in 1976,[10] the same year a funding code for the project was incorporated into the national budget under Konstantinos Karamanlis.

[13] In 1987, the University of Thessaloniki Transport Engineering Laboratory, under Vasilios Profillidis, published a proposal for an extensive, multi-branch light metro system, envisioned to be underground only between the New Railway Station and Sintrivani, at a cost of ₯28 billion ($555 million today).

[16][17] Although construction was scheduled to end in 1995, the project stalled and the unfinished (but excavated) initial cut-and-cover section became known as "the hole of Kouvelas" (Greek: η τρύπα του Κούβελα).

[18] Kouvelas resigned as mayor in order to become Minister for Public Works in the national government after the 1989 elections, and made Thessaloniki's newly-created municipal radio station, FM 100, responsible for the project's funding via ad revenue.

[19] The project also suffered due to intense political polarisation between New Democracy (of which Kouvelas was a member) and the Panhellenic Socialist Movement (PASOK) during the 1980s,[20] with the PASOK-led neighbouring municipalities of Kalamaria and the western suburbs also refusing to support the project,[21] leading to a metro design that ran exclusively within the limits of the New Democracy-dominated Municipality of Thessaloniki (the modern Line 1).

[21] In 1992 the government of Konstantinos Mitsotakis attempted to finance the project under a concession contract with a contractor budget of ₯65 billion ($743 million today).

[24] The European Ombudsman, Jacob Söderman, carried out a two-year investigation into the matter, the most complicated in his office's history, and sided with Makedoniko Metro on the issue of inadequate communication on the part of the Commission,[35][36] but otherwise rejected its legal arguments.

[37] With the contract commencement deadline approaching in 2002, Thessaloniki mayor Vasilis Papageorgopoulos, along with representatives from 130 city-based organisations, requested an emergency meeting with Prime Minister Simitis as well as the President of Greece, and threatened a mass rally to protest the potential cancellation of the project.

[16] With the failure of the concession model, in September 2003 the Ministry of the Environment, Urban Planning and Public Works under Vasso Papandreou decided to tender the metro as a public work,[40] co-financed by the Greek government, the European Union's Regional Development Fund, and loans from the European Investment Bank (whose vice-president at the time, Plutarchos Sakellaris, was a Thessaloniki native).

[53] Today, many antiquities discovered due to the construction of the line are on display at permanent in-station exhibitions, while the major discoveries can be found at station Venizelou.

[43] It was expected that the line would enter service in its entirety, between New Railway Station and Nea Elvetia in 2020 but will not stop at Agias Sofias and Venizelou, which were planned to open at a later date.

[55][56] By February 2019 construction on the main line was 95 percent completed and platform screen doors were beginning to be installed, while the Supreme Council for Civil Personnel Selection was planning a competition to fill the first 28 Thessaloniki Metro employee positions.

[57] Despite the progress, in September 2019 Greece's new conservative cabinet announced a further 28-month delay to the project, pushing the opening date from November 2020 to April 2023 and citing costly archaeological works at Venizelou as the reason.

The decision to disassemble the archaeological finds, dubbed a "Byzantine Pompeii",[61][62] was strongly criticised, and a citizens' group has taken the government to court over the issue for a second time, supported by former mayor Yiannis Boutaris among others.

[64] In April 2020, the International Association of Byzantine Studies (AIEB) wrote to Prime Minister Mitsotakis to protest the removal of the antiquities from their original location, saying that the discoveries constituted "a cultural and scientific jewel" and that "it would be a tragedy to jeopardise [Greece's reputation for monument preservation] by squandering the treasure of the Thessaloniki material and data through an unnecessarily hasty construction project", arguing that the previous decision to leave the discoveries in-situ was preferable.

[62] In a customer satisfaction survey carried out by the Aristotle University of Thessaloniki in the months prior to the inauguration of the metro, the only such survey to be published in a peer reviewed journal, 85% of respondents viewed the construction of the metro positively, but also showed overwhelming support for the notions that poor planning and inefficient management of funds were a cause of the years-long construction delays.

[65] A different study found that, even though there was widespread dissatisfaction with the construction works and associated years-long traffic arrangements, as well as the closure of businesses that resulted from these, there was also a high degree of understanding of and support for the city's transit-oriented development model.

[74][75] Nevertheless, use of the metro in the first few days of fare-free operation was high, with employees needing to deploy crowd control measures to prevent platform overcrowding.

Similar in construction to Line 1, it has two parallel single-track tunnels on a 4.78 km (2.97 mi) route between 25 Martiou and Mikra and adds five stations to the network.

After confusion about the extension's place in the system, Elliniko Metro clarified in August 2018 that it would be a separate line running between New Railway Station and Mikra without the need to change trains at 25 Martiou.

[80] The extension to the northwestern districts initially included a circular line and was in a preliminary phase[82][83][84] until the fall of 2023 when the management of Elliniko Metro S.A. decided not to proceed with the project, considering it both structurally unfeasible and wrong in design.

[90] The overground parts of the line will probably stand at a height of 5 meters and on a bridge in order to avoid further delays due to possible archaeological finds.

[112] In preparation for the start of operations on 30 November 2024, Minister of Infrastructure and Transport Christos Staikouras revealed the system's brand identity.

[114] The company retorted that the second competition was cancelled due to not being satisfied with the bids received (8 in total), eventually deciding to award the €30,000 prize money to a company directly in order for the visual identity to be ready on time,[117] while the Architects' Association of Thessaloniki accused the company of deliberately orchestrating the situation in order to give the contract to an "obscure start-up which did not even have a website at the time of its appointment",[118] a situation it described as "a sham process - at the expense of fellow architects and other related professionals (graphic designers, artists) and ultimately the local community" as part of a "long list of direct appointments".

[120] Elliniko Metro amended the metadata five hours after the official unveiling of the logo, changing among others the name of the author, but had already disseminated the unaltered presentation to media outlets such as Naftemporiki.

[124] Other important discoveries included a headless statue of Aphrodite, fourth-century-AD mosaics, a golden wreath, a bath complex, urban villas, and 50,000 coins.

In the past, Thessaloniki Metro was regularly the subject of a number of jokes in Greece due to its successive construction and operation delays.

[8][141][142] A fictionalised version of Sintrivani station (under the older name of Sintrivani/Ekthesi) was depicted in the film The Bricklayer, which was set in Thessaloniki, prior to the metro system becoming operational; this drew laughter from cinema audiences in the city.