The company beat estimated American Depository Share earnings, but missed revenue estimates. Revenue was up 29 percent over this quarter last year.
The stock declined mostly due to lower-than-expected guidance for revenue for next quarter.
Revenue was projected to be RMB 22.2 billion ($3.35 billion), compared to a Thomson Reuters consensus estimate of RMB 24.8 billion ($3.73 billion).
"In the third quarter, we made good progress in our strategic pillars to strengthen our mobile foundation and lead in AI," Baidu co-founder and Chief Executive Officer Robin Li said in a press release.
"On strengthening our mobile foundation, our strategy to leverage Baidu's leading AI technologies to increase the user scale and user stickiness of Mobile Baidu is showing measurable results. On our AI initiatives, we continue to focus on developing platforms for smart device and autonomous driving markets, as well as leveraging AI into vertical sectors, such as financial services," Li said.