Shares of Google, which have increased roughly 5 percent since Monday, slid 3.1 percent to $576.92 in after-hours trade on Thursday.
Google posted net income of $1.96 billion, or $6.06 a share, compared with net income of $1.42 billion, or $4.49 a share, in the year-earlier period.
Excluding certain items, Google said it earned $6.76 a share, beating the $6.60 average forecast by analysts polled by Thomson Reuters I/B/E/S.
The Mountain View, California-based company, which controls roughly two-thirds of the U.S. search market, said revenue in the first quarter totaled $6.77 billion, compared with $5.51 billion in the year-ago period.
Net revenue, which excludes costs that Google pays to partner websites, was $5.06 billion, up 2.2 percent from the seasonally strong fourth quarter and above analysts' average estimate of $4.95 billion.
(Reporting by Alexei Oreskovic; Editing by Richard Chang)