Grabarz, a relatively late developer who has emerged as an international class competitor aged 25, was a cut above the rest in the early jumps, although he had to win on count-back as Lithuania's Raivydas Stanys managed to equal his jump of 2.31 metres with a personal best.
The Londoner, who leapt to a world-lead 2.36m in New York earlier in June, goes into the London Olympics as a genuine medal contender and an outside bet for gold.
"There’s a big smile on my face, it feels great to have got the gold," said Grabarz.
"I had a lot of fun and I learnt a lot about myself, I learnt about dealing with the pressure and the expectations around myself.
"I wanted to be as clinical as possible, clearing the earlier heights at the first time of asking and that’s what clinched it in the end.
"I wanted to make it as hard as possible because that is only going to help me when the Games come around."
Welshman Williams, meanwhile, ran a controlled race in the 400m hurdles, winning from young Serb Emir Bekric in 49.33 seconds.
It was a double boost as the victory means he joins compatriot and training partner Dai Greene at the Olympics: Jack Green had been selected to accompany world champion Greene in London, but the third discretionary spot was up for grabs between Williams and Nathan Woodward, who finished seventh.
"The feeling is one of relief more than anything. I have European bronze, I've won European silver and I've won the juniors, I didn't think it would take me nine years to win a senior title though," Williams said.
"I really wanted to make the most of this opportunity, I always wanted to come here and treat it like a major championships and try and win.
"This is a stepping stone, I know I can go a bit quicker because I clipped a couple of hurdles."
It was a decent day for the Brits in the end as Sharp grabbed a surprise silver in the women's 800m, sneaking in after the pace-setters Irina Maracheva and Maryna Arzamasava both cramped up in the home strait. Russia's Yelena Arzhakova won gold in 1:58.51.
Sharp's silver gives Team GB a selection dilemma: she has failed to reach the A-time for automatic qualification, but a personal best of 2:00.52 means she is hitting form at the right time.
Goldie Sayers was not so fortunate though as her shot put throw of 63.01 was only enough for fourth. Vira Rebryk of Ukraine took gold with a monster fifth-round throw of 66.86, a national record.
And Lee McConnell finished fifth in the women's 400m, which was surprisingly won by Sweden's Moa Hjelmer with a national record of 51.13s.
Meanwhile, British 200m duo Daniel Talbot and Chris Clarke both qualified for the men's final, although Abi Oyepitan failed to make the women's medal race.
Defending champion Mahiedine Mekhissi-Benabbad won the 3,000 metre steeplechase gold medal at the European athletics championships in Helsinki on Friday after Spain's Victor Garcia fell at the last barrier.
Garcia, who had timed his late run to catch the leading Frenchman, still got up in time to claim the bronze, but lost out on a silver medal to Turkey's Tarik Akdag.
"I slowed down at the last moment and I fell," Garcia told reporters. "I just wanted to get up as quick as possible and I don't really know what happened there."
Veteran German shot putter Nadine Kleinert finally claimed her first European gold medal after seeing off the challenge of Russia's Irina Tarasova.
An Olympic and three-times world championship silver medallist, Kleinert threw 19.18 metres to strike gold.
Fellow German Betty Heidler could only finish 17th in the hammer, missing out on the final. Her best throw of 65.06 metres was over 14 metres short of her world record 79.42, set last year.