The Killing star will play a new love interest for Castle (Nathan Fillion), according to TV Line.
Lehman's character, a sophisticated art insurance investigator with a mysterious past, is initially intended for a one-off appearance but could recur in future episodes.
Lehman currently plays Gwen Eaton on AMC's The Killing and has also appeared in episodes of Human Target, Prison Break and The X-Files.
The actress also previously starred opposite Castle's Nathan Fillion in short-lived Fox drama Drive.
Die Hard star William Atherton and Star Trek actor Michael Dorn have also won roles in the new season of Castle.
The comedy-drama returns to ABC on Monday, September 19 at 10/9c.
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