Edwards is to reprise his role for the Nov. 18 installment of the show's 15th and final season, the network announced Thursday.
Greene will be seen in a series of newly shot flashbacks, featuring other former staff and offering insight into Dr. Banfield's (Angela Bassett) past and her experiences at County General.
"We had hoped to bring back some of 'ER's' stars for the final season and think that our loyal fans will enjoy seeing some of the show's most beloved and memorable characters," executive producer John Wells said in a statement.
Edwards first appeared in the "ER" pilot and, after nearly eight seasons, completed his run in a highly rated episode, in which his character died, at the end of the 2001-02 television season.
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