Eurolink Motorway Operation (M3) Ltd recorded profits for 2011 of €41.6m -- compared to just over €19.4m in 2010.
The company operates the M3, which stretches 50km from Clonee to north of Kells and cost €1bn to build.
The road itself was subject to major controversy in 2010 as its construction took it close to the Hill of Tara, sparking protests and court challenges.
But according to accounts filed this week, the firm has almost doubled its profits.
The accounts show that despite the economic woes, more drivers are using the motorway.
The company reported that its "daily traffic volumes" increase by 8.3pc.
Drivers pay a toll of between 70 cents and €3.40 to use the motorway.
The company notes in its accounts that the toll fare has remained the same both last year and in 2010.
However, it is yet to reveal whether it will increase tolls from next year.
The National Roads Authority (NRA) has already warned that tolls on a number of the country's motorways will rise by at least 10 cents.
"Tolling in Ireland is regulated in line with inflation. Therefore tolls cannot go beyond inflation," an NRA spokesman told the Herald.
The news comes after increases in the price of petrol coupled with the revelation that the price of using public transport is also set to rise.
Bus and rail fares across Ireland are to soar by as much as 18pc within weeks -- with Dubliners hit the hardest.
Car tax is also certain to increase in the Budget 2013, Government sources admit.
Fianna Fail Transport spokesman Timmy Dooley said he feared 2013 would be the "bleakest year yet" for Irish motorists.
"It's very difficult to see these firms record massive profits when motorists and transport firms are braced for extra costs left, right and centre.
"How much more does the Government think motorists can afford?"