Neither of the big-name players contributed much to a feisty encounter until Ronaldo stooped to meet Miguel Veloso's pinpoint cross from the left with an intelligent header in the 82nd minute.
Until then, Ronaldo had struggled against a massed Swedish defence, wasted two free kicks by firing into the wall and been booked shortly before his goal for a foul on goalkeeper Andreas Isaksson as his frustration boiled over.
Sweden had several chances in the first half before Portugal took control after the break at the Luz stadium, gaining the upper hand for Tuesday's second leg in Stockholm.
"We would have been very happy with a draw," Sweden coach Erik Harmen told TV4. "We played a good game defensively, the goal was unnecessary, we were careless with that cross."
Portugal could have gone ahead in the opening minutes when Raul Meireles put Joao Moutinho clean through only for the Monaco midfielder to shoot into the side-netting.
The Swedes then enjoyed a brief period of dominance and came close when Johan Elmander just failed to hit the target from a pinpoint cross by right back Mikael Lustig.
Ibrahimovic was mostly left alone upfront, making him easy prey for the Portuguese defence.
His only real flash of inspiration was a dummy which created a clear shooting chance for Sebastian Larsson, whose effort was turned away by Rui Patricio.
Portugal were also hugely relieved to see Kallstrom blast a close-range free kick narrowly wide.
The hosts then won a flurry of corners which produced little apart from a Ronaldo header over the bar.
The Swedish fielded a very experienced side with more than half of their starters in their thirties, many of them with the last chance to play a World Cup.
Portugal coach Paulo Bento, in turn, stuck to his routine line-up, with Veloso and Moutinho the midfield combatants while Nani and Helder Postiga completed the attacking trio alongside Ronaldo.
Portugal dominated the second half although they did not create many clearcut chances until Ronaldo's goal. That brought them to life and Ronaldo headed against the bar in the dying minutes.
(Reporting by Daniel Alvarenga; Editing by Brian Homewood)
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