The Breaking Bad star will play two roles in the fantasy series, according to TV Line.
In the show's real-world segments, Esposito will play Sidney, a newspaper reporter who eagerly serves Regina (Lana Parrilla).
He will also appear in Once Upon a Time's fantasy sequences as the face of the magic mirror used by The Evil Queen (also played by Parrilla).
The actor currently plays drug lord Gus Fring on AMC's Breaking Bad and has also appeared in episodes of CSI: Miami, Leverage, Detroit 1-8-7 and Criminal Minds: Suspect Behaviour.
Former House star Jennifer Morrison, Big Love actress Ginnifer Goodwin and Robert Carlyle will also appear in Once Upon a Time.
The series premieres on Sunday, October 23 at 8/7c on ABC.
> ABC exec: 'Once Upon A Time similar to Lost'
Watch a trailer for Once Upon a Time below: