According to the American Consumer Satisfaction Index, customer satisfaction score rose by 4% to 79, while fell by 3.7% to 78 -- the second consecutive yearly decline.
Other search engines measured in the rankings were , which posted the biggest increase to score 75, making it equal with . dropped by 9% to record a satisfaction score of 67, making it the biggest loser in the survey.
The boost to Yahoo! follows the relaunch of its main site, and developments of other community sites such as photography sharing site Flickr, and YouTube rival Yahoo! Video.
Yahoo! will welcome the good news, because the company has been through a period of upheaval during which chief executive Terry Semel stepped down in June and its share price dropped to its lowest level since March 2004.
Larry Freed, president and CEO of ForeSee Results, which sponsored the research, said: "Even more important than Yahoo!'s first lead over Google is the trend of their scores moving in opposite directions.
He added that the index was an indicator of financial performance in the wider business world, saying "we may see a real turnaround for Yahoo! in the next year".
The ACSI reports scores on a scale of zero to 100 across 10 economic sectors, 43 industries and 200 companies.