The 27-year-old German led the way as his team locked out the front row of Saturday's grid but he was immediately concerned afterwards that he does not endure a repeat of his problems at last month's Bahrain Grand Prix where he limped home ninth.
"I had a really good lap at the end and it is great motivation for the team but we have to be cautious because of what happened in Bahrain," he warned.
"Everybody's been working hard back in the factory. We will face different issues with the tyres than we did in Bahrain, but it will still be a big challenge with the tyres tomorrow."
Rosberg clocked a dazzling best lap time of one minute and 20.718 seconds to outpace his nearest rival and Mercedes team-mate Lewis Hamilton by two-tenths of a second.
After poles secured by Hamilton in China and Rosberg in Bahrain, this was a magnificent treble top for the resurgent Mercedes outfit as they outclassed their rivals at the Circuit de Catalunya.
Defending triple world champion Sebastian Vettel gave his best for Red Bull to qualify third ahead of Kimi Raikkonen for Lotus, local hero and two-time champion Fernando Alonso and his Ferrari team-mate Felipe Massa.
Hamilton said: "Congrats to Nico - I'm really happy for the team. It's down to all the great work from the guys at the factory. But we've got to approach tomorrow with caution because it's going to be tough.
"I didn't have two options tyre sets, but I think Nico was quicker today."
Vettel said: "I was pretty pleased with the last sector because in the past it has been poor for me. It will be an interesting race and will be all about the tyre degradation.
"The tyres seem to not last as long as we would like but we're happy to be in a good position for the start of the race."
For Mercedes it was an auspicious afternoon as only once in 22 races at the Spanish track has a driver who did not start from the front row managed to win - and that was seven-time champion Michael Schumacher for Ferrari back in 1996.
Romain Grosjean was seventh in the second Lotus ahead of Mark Webber in the second Red Bull, Sergio Perez in the leading McLaren and Paul di Resta of Force India.
McLaren team-mate Jenson Button flopped again and qualified only 14th despite major modifications to their car.
At the bottom end of the field, last year's triumphant Williams team saw both of their drivers fail to make the cut to Q2 and Venezuelan Pastor Maldonado, on pole in 2012 before winning the race, exiting after claims from Button that the Latin American had blocked him.
The Williams team's newly-appointed deputy team chief Claire Williams said: "It's not why we come racing - to not get any drivers into Q2, but we are not going to panic. It's so competitive in F1 these days."
Maldonado said: "It's so different to last year... It is so difficult to do my best and the car is difficult to drive. It is a worrying situation."
It was a desultory day for Button who not only failed to beat his team-mate, but also failed to make the cut and wound up 14th and eliminated.
Nico Rosberg cautious despite Spanish Grand Prix pole
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