The first E721-0 series sets were delivered from December 2006, and entered service on 1 February 2007 on Tohoku Main Line services.
The first E721-500 and SAT721 series sets were delivered from February 2006 and entered service on Sendai Airport services on 18 March 2007.

Two sets, P-1 and P-19, were derailed and badly damaged by the 2011 Tōhoku earthquake and tsunami on 11 March 2011 while at Shinchi Station, and were withdrawn.

The first of a fleet of 19 new four-car E721-1000 sets (76 vehicles in total) was introduced on 30 November 2016 on Tohoku Main Line, Joban Line, and Senzan Line services, replacing older 719 series units.
The new trains are built by J-TREC, with construction shared between the company's Yokohama and Niitsu factories.
These trains feature LED interior lighting.

The first four E721-1000 series intermediate cars were delivered from J-TREC's Niitsu factory to its Yokohama factory in September 2016 to be combined with driving cars built there.

In order to replace their 8100 series trains, Abukuma Express announced the order of new AB900 series trains in summer 2018.
They are based on the E721 series, and are the first new trains for Abukuma Express since 1988.
The first AB900 series set was delivered in February 2019.
It entered service on 1 July 2019.
The first E721-0 series sets were delivered from December 2006, and entered service on 1 February 2007 on Tohoku Main Line services. The first E721-500 and SAT721 series sets were delivered from February 2006 and entered service on Sendai Airport services on 18 March 2007.
Two sets, P-1 and P-19, were derailed and badly damaged by the 2011 Tōhoku earthquake and tsunami on 11 March 2011 while at Shinchi Station, and were withdrawn.
The first of a fleet of 19 new four-car E721-1000 sets (76 vehicles in total) was introduced on 30 November 2016 on Tohoku Main Line, Joban Line, and Senzan Line services, replacing older 719 series units. The new trains are built by J-TREC, with construction shared between the company's Yokohama and Niitsu factories. These trains feature LED interior lighting.
The first four E721-1000 series intermediate cars were delivered from J-TREC's Niitsu factory to its Yokohama factory in September 2016 to be combined with driving cars built there.
In order to replace their 8100 series trains, Abukuma Express announced the order of new AB900 series trains in summer 2018. They are based on the E721 series, and are the first new trains for Abukuma Express since 1988. The first AB900 series set was delivered in February 2019. It entered service on 1 July 2019.
E721 series