Hamilton clocked in with a time of one hour, 35 minutes and 29.972 seconds at the Circuit de Barcelona-Catalunya, over 20 seconds ahead of fellow Mercedes driver Valtteri Bottas of Finland, reports Efe.
However, Ferrari's really issues started on Lap 25 with Raikkonen retiring.
With Vettel some way off Hamilton's pace and Kimi Raikkonen forced into retirement by an engine problem, the biggest challenge to Mercedes threatened to come from Red Bull's decision to adopt a one-stop strategy.
"I'm always on the worrying side and we'd been very good in winter testing here and when we went to Melbourne everybody said it was going to be an easy Mercedes one and then we had hard races so I think we were very good today but we need to stay calm and humble", Wolff said.
Grosjean, once labelled a first-lap nutcase by Mark Webber, lost control of his Haas at Turn 3 and slid back across the track in a cloud of tyre smoke.
Korea to hold ceremony May 23-25 over dismantling nuclear test site
The nuclear facility was hidden in Mount Mantap and suffered multiple landslides following the bomb tests. Confirmation of the meeting between the two men came after landmark talks between North and South Korea.
"I remember like it was yesterday sitting at home playing this computer game as Michael", Hamilton said.
Lewis Hamilton said he will "sleep like a baby" after claiming a convincing victory at the Spanish Grand Prix. "It's a shame it's only four hundredths but for us as a team, flawless result today".
Both Ferrari men delivered sloppy first runs en route to pole position, but because of that, they should have been back on track, on the Super Softs, when their final runs commenced. You saw that it worked out for [Daniel] Ricciardo and Verstappen in Shanghai, I think this is what they were thinking. "Strength in depth. I hope it can continue".
In Spain, though, he took his first pole since Melbourne - albeit by a tiny margin from the on-form Bottas - and walked the race, even if he may not have had it quite so easy had his team-mate not got jumped by Vettel at the start.
Grosjean, who struggled throughout the weekend, couldn't stop his vehicle from spinning across the track on Turn 3 and Hulkenberg and Gasly could not avoid colliding with him. Bottas had done enough on track to move back ahead of the Ferrari only for a sticky rear tyre to contribute to a slow stop and leave Vettel running ahead. It was gutsy, especially after the criticism they received after failing to take advantage of the safety auto to pit Hamilton in China.
UFC 224 Post-Fight Press Conference
I do give Machida a slight edge, but the tide could easily shift to either side when two legendary champions like these collide. Pennington has quietly put together a four-fight win streak, notably taking down Jessica Andrade and Meisha Tate along the way.
The Brit gave praise to the Mercedes team though, saying it was not all his work. What had looked at first sight like questionable strategy was actually, they said, just the vehicle going through its tyres quicker than others.
All eyes now turn to Monaco for arguably the most iconic of the season's races on May 27.
Vettel will be desperate to get back to winning ways after finishes of 8th, 4th, and 4th in his last three races have seen him drop to 17 points behind Lewis Hamilton in the leaderboard.
USA to help N Korea's economy if it abandons nuclear weapons
Vice President Mike Pence praised Kim Jong Un for making moves toward peace, but expressed caution. To the U.S. , that means the North giving up the nuclear weapons it has already built.