The category was one of many that honoured the best in fleet in the Fleet News Awards, run by Fleet News Europe's sister-title.
Wilsher, based at AT&T's offices in Worcestershire in the United Kingdom, received his award at a ceremony attended by more than 1,200 automotive and fleet industry executives at Le Meridien Grosvenor House Hotel in London this month.
He said: 'This award is not a reflection of a solo effort, it is a reflection of my two excellent team members, Joanne Paul and Jane Amos, without whom AT&T fleet management would never have achieved so much.
'Pan-European fleet is a difficult and diverse market and you have to balance so many things. Having strong business partnerships is the key to success, as is having a great team.'
AT&T operates 900 vehicles in the Europe, Middle East and Africa (EMEA) regions, with the United Kingdom having the largest fleet of 430 vehicles, followed by The Netherlands with 180 vehicles.
The remainder is spread across more than 20 other countries and until two-and-half years ago AT&T's fleet operations were run autonomously.
It was around that time that AT&T increased its fleet size by acquiring IBM Global Network Services.
The fleet consolidation involving so many countries, vehicles and suppliers was a tough job.
Today, AT&T uses leasing alliance EFFAM, which has leasing company members in 17 different countries and a combined fleet of 270,000 cars.
In the UK, AT&T uses EFFAM partner HSBC Vehicle Finance and Arval PHH, which is also a preferred supplier in Austria, Belgium, France, Germany, Italy and Switzerland.
In the Netherlands, AT&T uses EFFAM's Dutch partner, TOP Lease. EFFAM and Arval PHH each supply about 40% of AT&T's fleet, and the remaining 20% are either outright-owned, for example the company owns half a dozen vehicles in Russia, or provided by local country suppliers.
As part of his entry to the awards, Wilsher said future developments will include the 'harmonisation of entities with each country, resulting in one fleet policy per country and established preferred supplier (s)'.