Though it had ruled out a diesel — once saying: "a Porsche that doesn't rev beyond 5000rpm isn't a Porsche" — the change of mind was spurred by new European tax incepntives for diesel vehicles.
It was further swayed by its majority shareholding in one of the world's biggest diesel-engine makers, Volkswagen.
From next year the Cayenne will be offered with an Audi-derived 3.0-litre V6 turbo-diesel with 176kW and 550Nm of torque. It is fitted only to a six-speed Tiptronic transmission.
Porsche claims 9.3 litres/100km and 244g/km of CO2 emissions.
It is the second Audi engine to be fitted to the Cayenne after last year's launch of the 3-litre petrol V6 and now brings to four the SUV's engine options.
Porsche will also make the Cayenne with a hybrid powertrain from 2010.
In a statement, Porsche revved up the diesel by stating: "The spontaneous throttle response and high torque characteristics of this diesel engine deliver the required performance levels for an athletic all-terrain vehicle such as the Cayenne."