The plunge comes after the business ratings and reviews company reported a big miss on first quarter earnings after the closing bell on Wednesday.
Yelp posted a loss of 2 cents per share, missing expectations for a 1 cent loss, on revenue that totaled $118.5 million, short of expectations for revenue of $119.8 million.
The company also posted a disappointing outlook for full-year revenues, at $574-$579 million against expectations for $579.2 million.
The stock fell to as low as $40.14 a share on Thursday, a level last reached in July 2013. It's now down 26% year-to-date, and 30% over the past 12 months.
Here's a chart showing the plunge in trading:
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