Briton Farah, challenged by Kenyan Paul Tanui, pushed to the front with 350m to go to defeat Tanui, who ran 26:51.86.
Geoffrey Kamworor, also of Kenya, took third in 26:52.65.
"It would have been good to run a little bit faster," Farah said. "Training has been going pretty well.
"But it was tough. It was difficult doing it all the way by yourself. The pacemakers the first couple of laps were spot on, then it slowed down a lot.
"We were just going back and forth and that's wasting a lot of energy," said Farah, who was hoping for a time in the 26:30 range.
His next race will be a 1,500m at next month's Birmingham Diamond League meeting.
"I don't know what is going to happen after that," said Farah, who is undecided on whether to try for another distance double at August's world championships in Beijing.
Ethiopian world junior champion Yomif Kejelcha stole the show in the men's 5,000m, running a lifetime best 13:10.54, also the year's fastest time.
The 17-year-old surged past Olympic 10,000m silver medallist Galen Rupp with 300m to go and won comfortably.
He had won the world junior championship on the same Hayward Field track last July.
Kenyan Edwin Soi claimed second in 13:11.97 and hometown favourite Rupp faded to third in 13:12.36.
Also on the first day of the two-day meeting, American long jumper Tianna Bartoletta became the first woman to leap over seven metres this year though her mark of 7.11m was wind-aided.
(Reporting by Gene Cherry; Editing by Peter Rutherford)
Share
