The German’s best time of 1m 24.939s eclipsed that of Mercedes' Lewis Hamilton by 0.470s, with both drivers setting their times on Pirelli’s medium-compound tyre.
At the lunch break, Valtteri Bottas was third fastest for Williams in the FW38, with Daniel Ricciardo moving his Red Bull RB12 ahead of stablemate Carlos Sainz’s unliveried Toro Rosso STR11 for fourth.
Jenson Button clocked an encouraging 35 laps in the Honda-powered McLaren MP4-31 as he went sixth quickest, but Hamilton was the morning's overwhelming lap leader, having clocked 66 trouble-free tours - the exact equivalent of a race distance in Spain.
The circuit had been damp when the first cars ventured out at 9.00am local time, following a number of unveilings in the pit lane. However, a dry line soon emerged and teams were able to switch to dry-weather tyres.
Romain Grosjean was quick to give the new Haas VF-16 its track debut after joining team mate Esteban Gutierrez to take the covers off the American team’s first ever car, and soon set an encouraging time of 1m 28.399s. However, the Frenchman was later responsible for bringing out the morning's only red flags when he lost his front wing on the pit straight, necessitating a clear up.
Grosjean ended up eighth on the timesheet at lunch with 13 laps under his belt, one place back of the C34 of Sauber’s Marcus Ericsson - the only driver not running in a 2016-spec machine.
Completing the initial leaderboard were the day’s three rookie runners - Alfonso Celis in the new Force India VJM09, Jolyon Palmer in the Renault R.S.16 and Pascal Wehrlein in the Manor MRT05, who was the only driver not to set a time.
Monday morning's unofficial testing times from Barcelona
|1||Sebastian Vettel||Ferrari SF16-H||1:24.939||36|
|2||Lewis Hamilton||Mercedes F1 W07 Hybrid||1:25.409||0.470||66|
|3||Valtteri Bottas||Williams-Mercedes FW38||1:26.091||1.152||43|
|4||Daniel Ricciardo||Red Bull Racing-TAG Heuer RB12||1:26.704||1.765||20|
|5||Carlos Sainz||Toro Rosso-Ferrari STR11||1:27.180||2.241||35|
|6||Jenson Button||McLaren-Honda MP4-31||1:27.691||2.752||35|
|7||Marcus Ericcson||Sauber-Ferrari C34||1:28.165||3.226||36|
|8||Romain Grosjean||Haas-Ferrari VF-16||1:28.399||3.460||13|
|9||Alfonso Celis||Force India-Mercedes VJM09||1:29.406||4.467||21|
|10||Jolyon Palmer||Renault R.S.16||1:31.351||6.412||15|
|11||Pascal Wehrlein||Manor Racing-Ferrari MRT05||1:33.455||8.516||8|