The CBS drama stars Jonny Lee Miller as a contemporary Sherlock Holmes solving crimes in New York, with the aid of his partner Joan Watson (Lucy Liu).
Bierko (Damages, Boston Legal) will play a Wall Street tycoon, TVLine reports.
His character Fowkes will be drawn into Sherlock's latest murder investigation in the show's fourth episode. Molly Price (Third Watch, Bionic Woman) will appear in the same instalment as Fowkes's executive secretary Donna.
The producers of Elementary recently ruled out a romance between Sherlock and Joan - calling such a development "completely off the table" - but did hint at the introduction of iconic villain Moriarty.
Elementary premieres in the US on September 27. In the UK, the series will air on Sky Living.
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Watch an Elementary behind-the-scenes video below: