The Jamaican world record holder, who managed only 10.04 in Ostrava last Friday, was back to his best against a world class field which included his compatriot and former world record holder Asafa Powell.
Powell, who said later he had not heard the starting gun, finished second in 9.91 while European champion Christophe Lemaitre finished strongly to take third place in 10.04 seconds.
Bolt said he had not been sleeping regularly since he arrived in Europe.
"After Ostrava I decided I will make sure to go to bed early and start eating right," he said. "I feel extremely well, so it's coming back and I'm feeling good.
"People expect me to do well all the time and I expect that from myself also, it's not really pressure for me. I came out here tonight not to prove anything but to tell myself I've still got it.
"The race was much better than in Ostrava. After Ostrava a lot of people questioned me but I never questioned myself."
Ethiopian Fantu Magiso upset Kenya's Olympic champion Pamela Jelimo in the women's 800 metres in a national record of one minute 57.56 seconds.
"This is a huge result for me," she said. "I expected that I could run very fast today because my coach told me that today was a good chance for me. This year I am training well and I want to take the chance at the Olympics."
Magiso's team-mate Abebe Aregawi also set a national record, clocking a season's best of 3:56.54 in the 1,500 metres.
Kenyan Paul Koech made a spirited attempt to break the men's world steeplechase record, setting the third fastest time ever with a time of 7:54.31.
"I was targeting the world record," Koech said. "During training I had the world record in mind.
"I hoped to achieve the world record here in Rome but I am not disappointed because I achieved a new personal best and now I am confident. I think I am capable of running the world record."
British high jumper Robbie Grabarz produced a world leading 2.33 metres to claim some high-profile scalps and win his first-ever Diamond League title.
Greg Rutherford won the men's long jump with a leap of 8.32m, just three centimetres off his British record, although team-mate and training partner Chris Tomlinson was disappointed with his 7.77m best.
Goldie Sayers threw a season's best 64.73m to finish third in a javelin competition won by world record holder Barbora Spotakova, with a world leading 68.55m
Great Britain's Yamile Aldama finished fourth in the women's triple jump as world leader, Colombia's Caterine Ibarguen, claimed third behind Ukrainian winner Olha Saladukha and second placed Olga Rypakova.
Meanwhile, Steph Twell ran a season's best 4:09.50, well outside the Olympic qualifying standard, to finish 12th over 1500m while Emma Jackson was a disappointing tenth in a high-quality 800m race.
Jo Pavey, back on the track after her failure to make the marathon team, was tenth in the 5,000m clocking 15:09.53, well inside the required Olympic standard.
In the absence of British world champion Dai Greene, Puerto Rico's Javier Culson won the 400m hurdles while Britain's Nathan Woodward ran a season's best 49.64 secs - although he'll need nearly a two tenth improvement to join the four British athletes who have already achieved the qualifying standard.