In its first earnings report since the firing of former chief executive Carol Bartz, the company announced that earnings had fallen to $1.07bn (£677m), down 5% on the $1.12bn a year ago.
Yahoo posted a profit of $293.3m, or $0.23 a share, down from $396.1m, or $0.29 a share, but analysts surveyed by Thomson Reuters had predicted a fall in per-share earnings to $0.17.
The company said that the year-on-year decreases in earnings were "primarily due to the revenue share related to the Search Agreement with Microsoft".
The search engine, which remains one of the most popular destinations on the internet, expects revenue of $1.13bn to $1.24bn in the final three months of the year.
"We're pleased that revenue, operating income and EPS were all above consensus this quarter," said Tim Morse, the chief financial officer and Interim chief executive at Yahoo.
"My focus, and that of the whole company, is to move the business forward with new technology, partnerships, products, and premium personalised content - all with an eye toward growing monetisation."
Bartz was fired in September after having failed to arrest the company's decline in market share to internet rivals Google and Facebook. Yahoo announced a strategic review after her dismissal, with widespread speculation that the $20bn firm could be the subject of a takeover bid.
Microsoft is thought to be preparing another proposal after it failed with a $44.6bn hostile bid for Yahoo in 2008, while Yahoo co-founder Jerry Yang is said to have been sounding out private equity groups about a management-led buyout.
Any new owner of Yahoo will have to rejuvenate the company that saw its share of the US search market slump to 16% in August, down from 19% two years ago, according to ComScore. In contrast, Google has remained the steady market leader at 65% and Microsoft's Bing engine had climbed to 15% from just 9% two years ago.
Yahoo said that its display advertising revenue was $449 million in the third quarter, which was flat compared to $448 million in the same period last year.
Emarketer has predicted that Yahoo's share of banner ads will be 13.1% this year in the US, down from 14.4% last year. It said that Facebook's share will climb to 16.3% from 12.2%, and Google is expected to account for 9.3%, up from 8.6%.