The Oban-born Williams star was in Barcelona with some of the biggest names in the sport.
She put in 73 laps in the car before she takes part in two Grand Prix practice sessions later this season.
But Wolff wound up on the timing screens faster than quadruple world champion Vettel as she finished in fifth place.
Her successful day will have done her bid to become Formula One's first female driver since Lella Lombardi in 1975 no harm at all.
Wolff's best time of 1 minute 27.280 seconds was less than a tenth of a second behind the Ferrari of 2007 world champion Kimi Raikkonen at the Spanish Grand Prix track.
She only made one mistake with a spin.
Wolff said afterwards: "I learnt a lot about how to drive these new look cars which are very different to previous seasons.
"I was then able to get some good mileage under my belt to understand the characteristics of the car and how to get the most out of this new style of power unit."
Vettel finished seventh in his Red Bull with a fastest lap of 1 minute 27.973s, despite completing 18 more laps.
Wolff, 31 - who is married to Mercedes F1 boss Toto Wolff - is now due to participate in free practice at Silverstone on July 4 before returning to the car in the same session at Hockenheim two weeks later.