Preston has signed up to appear in an episode of the crime drama in November, TV Line reports.
The actress, who is possibly best known for her role as Arlene in True Blood, is expected to play the aunt of a rape victim.
In a separate November instalment, Busfield will star as a widower whose fiancé, played by Miko, has disappeared.
Busfield has previously worked on shows like The West Wing, thirtysomething and Studio 60 on the Sunset Strip, while Miko's television credits include The Cape and Deadwood.
Law & Order: SVU airs on Wednesdays at 10/9c on NBC.
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