The line color on maps, station signs and train livery is tyrian purple (京紫, kyō-murasaki), derived from the kasaya robes worn by Buddhist monks.

Ridership, though less than half the numbers of the busiest Midōsuji Line, is still the second-highest of all lines in the Osaka Metro network, thanks to the large number of government buildings in eastern Chūō-ku and schools around Tennōji (total ridership for fiscal year 2009 was approximately 480,000 per day).

It runs completely underground from Dainichi to just before Yaominami, and was known as the longest continuously underground subway line in Japan for a long time after the opening of Yaominami Station (it was also among the longest subway tunnels in the world at the time of its opening).

Until 2016, heavier train maintenance and inspection were carried out by the same group in charge of Chūō Line trains, at the Morinomiya depot and workshop, accessible through a spur located before Tanimachi Rokuchōme Station on the Tanimachi Line and after Tanimachi Yonchōme Station on the Chūō Line (the Dainichi and Yao depots are used mainly to store off-service trains).

According to the original plan laid out for the Tanimachi Line in 1927, it was to follow Matsuyamachi-suji (to the west of Tanimachi-suji).

A second tunnel was dug at Umeda for this purpose, but the connection southwards was plagued by collapses and other accidents; as a result, the planned route was changed to the current one, stopping at Higashi-Umeda and then veering eastward.

Over the course of tunnel construction for the line, the underground waterways in Osaka were greatly altered, causing a number of incidents in which famous wells dried up.

Compared to the majority of areas served by the subway, where it runs underneath major roadways with high levels of traffic, part of the Tanimachi Line runs underneath relatively narrow streets with fewer cars, near residential areas.