Delany and "Castle" leading man Nathan Fillion played husband and wife on another ABC series, "Desperate Housewives."
The network said Delany is expected to appear in a two-part episode of "Castle" set to air March 21-22.
She is to play Federal Agent Jordan Shaw, "an insightful and accomplished federal investigator who teams with Richard Castle and Detective Beckett to hunt down a cunning and elusive serial killer," ABC said in a release.
"We're thrilled to have the opportunity to work with such a talented and versatile actress as Dana," "Castle" creator/executive producer Andrew Marlowe said in a statement. "She and Nathan were so great together on 'Desperate Housewives,' we're all excited to see them together again."