The first models will arrive in UK showrooms in summer 2010 with a choice of five engines and four trim levels.
The entry level option is the 1.4-litre 120bhp petrol, followed by the low-CO2 1.4-litre MultiAir option. The range-topping 1750 TBi 235bhp petrol will be available only on the classic Alfa Romeo Cloverleaf specification.
Alfa will also offer two diesel engines in the form of a 1.6 (105bhp) and 2.0-litre (170bhp) Multijet units.
In addition, the Giulietta is available in the same Turismo, Lusso and Veloce specifications offered with the recently released MiTo city car.
All models will be fitted with fuel consumption-reducing Start&Stop technology, air conditioning, LED front and rear lights and six airbags.
Alfa Romeo has installed its DNA technology in all models. The system monitors and adjusts brakes, suspension and steering to adapt the Giulietta to the road conditions.
At the top of the range, the exclusive Cloverleaf costs £24,495 and adds 18" alloy wheels, dark tinted windows, red painted brake calipers and the Cloverleaf badge.
The powerful petrol engine in the Cloverleaf powers it to 62mph from standing in 6.8 seconds and a top speed of 150mph.
The Giulietta is cheaper than the rival Ford Focus, and the all-new Compact platform has improved handling and steering, claims Alfa.
The new Giulietta will appear in public for the first time at the Goodwood Festival of Speed on 2-4 July, where the Italian manufacturer will be celebrating its 100 year anniversary with a range of classic models.