The "3rd Rock From the Sun" star will resurrect Arthur Mitchell, aka the Trinity Killer, for a brief appearance in the TV revival, according to Deadline.com.
It's unclear how Lithgow's character will factor into the new storyline as Mitchell was murdered by Michael C. Hall's Dexter in the original season four finale, which aired in 2009.
Lithgow, who won an Emmy and a Golden Globe for his portrayal of Mitchell, joins Hall in the show's upcoming season nine, which will be a 10-episode limited series from writer/producer Clyde Phillips.
Hall played the title character, a Florida police detective with a dark, secret life, from 2006 to 2013.
Michael C. Hall previously admitted he was not completely satisfied with the finale.
"I thought it was narratively satisfying - but it was not so savoury," he shared his opinions about the swan song. "I think the show had lost a certain amount of torque. Just inherently because of how long we'd done it, because of the storytelling capital we'd spent, because our writers may have been gassed… Maybe some people wanted a more satisfying… ending for him, either a happy ending or a more definitive sense of closure."
However, in a separate interview, showrunner Clyde Phillips insisted it's "not why [they're] doing" the reboot.
"We're doing this because there is such a hunger for Dexter out there," he claimed. "We're not undoing anything. We're not going to betray the audience and say, 'Whoops, that was all a dream.' "