HBO has confirmed Lohan will indeed be appearing on the series but declined to describe the role she would be playing.
Filming on the final eight-episode fourth season of the comedy series began in June in North Carolina. On Tuesday, Lohan posted a self-portrait on her Instagram feed with the note, "Back@work! So grateful today!"
According to E! Online, Lohan is playing the daughter of one of the show's main characters, who is the bride at her own wedding in a scene set far in the future.
The action of the show's fourth season is expected to pick up several years after the conclusion of season 3, which saw former major-league baseball player Powers getting back to the majors only to have a change of heart, fake his death and return to April, the mother of his child.
The new season of "Eastbound & Down" debuts on Sept. 29.