The mother of Joan Watson (Lucy Liu) was previously referenced in the show's pilot episode, when Sherlock (Jonny Lee Miller) learned that she had taken Joan's father back after an affair.
"Mum will meet Sherlock," exec producer Rob Doherty told TVLine. "Given what we know about mum - or heard about mum - and given what we know for sure about Sherlock, you can see it going a certain way. I feel like we're going to tell a story with a few lovely, little surprises."
Watson's mother will appear in the CBS drama's ninth episode, currently scheduled to air on December 13 in the US.
Foh Shen has previously played recurring roles on ABC medical series Gideon's Crossing, family drama Everwood and CBS crime procedural Close to Home, with guest stints on the likes of 24, Desperate Housewives and Boston Legal.
Other upcoming guest stars on Elementary include former House star Lisa Edelstein and The West Wing actor Roger Rees.
The series airs on Thursday nights on CBS and on Tuesdays on Sky Living in the UK.
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Watch a clip from Elementary below: