The firm said late on Tuesday that fourth-quarter profit rose by 82% to $372.2m (£209m), or $1.22 per share. Analysts had expected $1.50 a share.
Google's stock fell $30.88 to $401.78 in New York amid concerns that the tech-industry giant may be overvalued.
Google's miss comes after rival Yahoo had also disappointed investors.
Since Google listed on the Nasdaq stock index in August 2004, its shares have enjoyed a stellar run that has seen them quadruple in value.
Wednesday's tumble wiped more than $9bn from the market value of Google.
But there is also some good news
It was not all bad news for Google, however. While profits may have missed, sales were in line and grew by 86% to $1.92bn as new features including its e-mail service Gmail helped it attract advertisers.