It serves the city of Osaka and the adjacent municipalities of Higashiosaka, Kadoma, Moriguchi, Sakai, Suita, and Yao.

This combination is heard in bilingual Japanese-English automated next-station announcements on board all trains, which also provide information on local businesses near the station.

An older branding (also used on the original tram network run by the city until 1969) is the "Mio-Den" mark, which depicts an old-fashioned depth-marker, (澪標, mio-tsukushi), the logo for Osaka City, over the kanji for electricity (電, den), short for “electric train” (電車, densha).

This mark is still present on newer trainsets and staff uniforms as Osaka Metro retained it as its monsho, as well as a connection to the subway network's roots.

However, on August 28, 2014, the Osaka Municipal Transportation Bureau met about creating the extensions of the later five of the six lines listed below, and have stated considering the current cost of the new extensions (and the possibly of privatization at the time), the government has also considered using light rail transit or bus rapid transit instead.

Provisions were put in place for such an extension when the Yumesaki Tunnel between Cosmosquare and Yumeshima was built in the late-2000s, but the then-state of the artificial island at the time of the bid (with only industrial facilities and a single convenience store for the workers) meant it would have been unlikely to proceed had Osaka not won said bid.

Osaka Metro charges five types of fares for single rides, based on the distance traveled in each journey.

On April 8, 1970, a gas explosion occurred during an expansion of the Tanimachi Line at Tenjimbashisuji Rokuchōme Station, killing 79 people and injuring 420.

[14][15] The gas leaked out from a detached joint and filled the tunnel and exploded when a service vehicle's engine sparked over leaking gas, creating a fire column over 10 metres (33 ft) tall that burned around 30 buildings and damaged or destroyed a total of 495 buildings.