The small, eye-catching city car has been named the best car for businesses in its category at the awards, which aim to honour the best models available for fleet operators in the UK.
Judges of the awards cited the fun nature of the car and its ultra-efficient engine technology as reasons for the award.
Steve Moody, editor of Fleet World and chairman of the judging panel, says: "The cheeky 500 proves time and again that it is a car people love, and with its innovative new TwinAir engine it offers thrills and efficiency in equal measure, taking the class leader even further ahead of the rest."
Fiat TwinAir technology was introduced last year and comprises an innovative two-cylinder engine delivering 84bhp.
The size of the engine means the Fiat 500 TwinAir is the first petrol engine to qualify for exemption from the London congestion charge and free UK road tax, something business users will appreciate.
However, the car also comes with Fiat’s MultiJet engine, a 1.3-litre turbodiesel unit delivering sub-100g/km CO2 emissions with 95bhp.
This, along with the car’s strong residual values, secured the title for the 2008 Car of the Year winner.
Elena Bernardelli, marketing director, Fiat Group Automobiles UK, said: "The Fiat 500 has continued to sell well to retail customers and has caught the imagination of large and small fleets too, so we are delighted to see further support from Fleet World in this excellent category win."
Prices for the Fiat 500 start from less than £10,000, making it one of the cheapest to buy fleet cars on the market.