Toei Mita Line through-running network

Through-running finally arrived on 26 September 2000, when the last 4.0 km segment from Mita to Meguro opened and completed the line. On the same day, mutual through-running with the Tokyu Meguro Line began. The four days prior had seen a preparatory timetable revision on 22 September 2000 that introduced driver-only operation and put Tokyu trains into service. A distinctive feature of this southern extension is that the Meguro–Shirokane-Takanawa section is shared infrastructure with the Tokyo Metro Namboku Line, which launched its own Meguro through-services the very same day; the two operators run over common track and platforms there, a unique arrangement on the Tokyo subway. As Tokyu extended its Meguro Line from Musashi-Kosugi to Hiyoshi on 22 June 2008, Mita Line through-services followed southward to Hiyoshi.

The network's largest expansion came on 18 March 2023, when the Tokyu Shin-Yokohama Line and Sotetsu Shin-Yokohama Line opened. Routed via the Tokyu Meguro Line, Mita Line trains began mutual through-running onto the new Tokyu Shin-Yokohama Line and one-directional through-running into the Sotetsu network, reaching Ebina on the Sotetsu Main Line and Shonandai on the Sotetsu Izumino Line, with a portion of trips turning back at Shin-Yokohama. The Sotetsu link was one-directional at launch because the Toei 6500 series was not yet Sotetsu-certified; only Sotetsu 21000 series and Tokyu cars worked through-services onto Sotetsu metals at the opening. To support eight-car operation for the longer runs, the Mita Line introduced its new 6500 series trains, which entered service on 14 May 2022, while Sotetsu's 21000 series began appearing on through-services from the 2023 opening. The result is a single corridor linking the Itabashi district of northern Tokyo, the central business districts along the Mita Line trunk, and the suburban Sotetsu network west of Yokohama.

During daytime hours, Mita Line trains run all-stations within the Mita Line itself; express running occurs only on the Tokyu side. A typical daytime hour sees trains continuing south via the Tokyu Meguro Line to Hiyoshi, with a portion running through to the Sotetsu network as far as Ebina (and some weekend trips to Shonandai), alongside trains that turn back at Shirokane-Takanawa. The Meguro–Shirokane-Takanawa section is also used by Tokyo Metro Namboku Line trains, which share the track and platforms there.

• 1968On 27 December 1968 the first segment of the Toei Mita Line (then Toei Line 6) opened between Sugamo and Takashimadaira; at this stage it operated as a self-contained subway with no through-running.
• 2000On 22 September 2000 a timetable revision prepared the line for through-running: driver-only (one-person) operation began and Tokyu trains started running on the Mita Line, though the still-unopened Mita–Meguro section was operated non-revenue.
• 2000On 26 September 2000 the final 4.0 km segment from Mita to Meguro opened, completing the line, and mutual through-running with the Tokyu Meguro Line began. The Meguro–Shirokane-Takanawa section is shared infrastructure with the Tokyo Metro Namboku Line, which began its own Meguro through-services the same day.
• 2008On 22 June 2008 the Tokyu Meguro Line was extended from Musashi-Kosugi to Hiyoshi, and through-running was extended south to Hiyoshi accordingly.
• 2023On 18 March 2023 the Tokyu Shin-Yokohama Line and Sotetsu Shin-Yokohama Line opened. Via the Tokyu Meguro Line, the Mita Line began mutual through-running onto the Tokyu Shin-Yokohama Line and one-directional through-running onto the Sotetsu network (initially Sotetsu 21000 and Tokyu cars only, as the Toei 6500 series was not yet Sotetsu-certified at the opening), reaching Ebina on the Sotetsu Main Line and Shonandai on the Sotetsu Izumino Line, with some trips terminating at Shin-Yokohama.