This sub-series represented a stop-gap for use from 1998 on the
Chūō–Sōbu Line until the full-production
E231 series trains were delivered, and a total of 17 ten-car sets (numbered 51–67) were delivered to Narashino Depot in Chiba. These sets differ noticeably from the other 209 series variants in having wide cars (compared to for earlier flat-sided stock), as well as LED destination indicators, replacing the earlier roller blind type. While externally similar in appearance to the later E231 series sets, the 209-500 series are distinguishable by their white cab fronts and lack of six-door cars. In November 2000, two sets (66 and 67) were transferred to the
Keihin–Tōhoku—
Negishi Line and renumbered 80 and 81. In December 2003, the Chūō–Sōbu Line sets were reallocated to Mitaka Depot and renumbered 501–515. Between 2005 and 2006, set 515 was lent to the Keihin–Tōhoku—Negishi Line as a spare during car maintenance. Between 2006 and 2007, three more sets (513–515) were transferred to the Keihin–Tōhoku—Negishi Line to replace the prototype
209-900/910/920 series trains and renumbered 82–84. From October 2008, following the introduction of
E233-1000 series trains on the Keihin–Tōhoku—Negishi Line, one set (80) was transferred back to the Chūō–Sōbu Line (as set 516) while the other four sets (81–84) were modified (with ATS-P/SN instead of ATC) and transferred to the
Keiyō Line (as sets 31–34). From September 2010 to January 2011, three former Keiyō Line sets (31–33) were reduced to eight cars and reliveried for use on the
Musashino Line, renumbered M71–M73, and entered service from 4 December 2010. while the remaining eight sets (C506–C512 and C516) were reduced to 8 cars and reallocated to the Musashino Line and renumbered M74–M77 and M81–M84. The last Chūō–Sōbu Line set, set C511, was withdrawn from service on 19 April 2019. All sets were refurbished between 2016 and 2019, when the GTO-VVVF traction system was replaced with an IGBT-VVVF traction system.
Set transfer history The following table shows the transfer history for each of the 17 sets.
Formations 10-car sets , one set (34) is allocated to Keiyō Depot for use on the Keiyō Line (and through services to the Sotobō and Uchibō Lines). The set is formed as follows with four motored ("M") cars and six non-powered trailer ("T") cars. • Cars 3 and 8 each have one single-arm pantograph. • Cars 1 and 10 have a wheelchair space. • Car 4 is designated as a mildly air-conditioned car.
8-car sets , 11 eight-car sets (M71 to M77, M81 to M84) were allocated to Keiyō Depot for use on Musashino Line (and through services to the Keiyō Line). These sets are formed as follows with four motored ("M") cars and four non-powered trailer ("T") cars. • Cars 2 and 6 each have one pantograph (single-arm on sets M71–M77, lozenge-type on sets M81– M84). • Cars 1 and 8 have a wheelchair space. • Car 4 is designated as a mildly air-conditioned car.
Previous formations Chūō–Sōbu Line 10-car sets (1998 to 2019) Keihin–Tōhoku—Negishi Line 10-car sets (2001 to 2009) File:JREast-209-500-Mitsu511.jpg|A Chūō–Sōbu Line 209-500 series train at Akihabara station in April 2009 File:209-500 URA82 keihin tohoku line.jpg|A Keihin–Tōhoku—Negishi Line 209-500 series in November 2008 File:Series209-500-Keiyo-Line.jpg|A Keiyō Line 209-500 series in October 2020 ==209-900/910/920 series==