Trial runs with the new engines have proved successful
Grand Central's Sunderland to King's Cross service has been dogged by delays and was due have started last year.
Problems with the delivery and refurbishment of rolling stock prevented the East Coast Main Line service launching as planned.
But the firm said it was now able to offer a limited service, with the first train departing at 0646 GMT on Tuesday.
'Checks and upgrades'
Grand Central will run one return service per day, with stops in Teesside and North Yorkshire, until 23 December. It plans to restart services again on 27 December, after a programme of track maintenance.
Managing Director Ian Yeowart said: "We expect to have the full timetable up and running by the middle of January, when all the rolling stock has gone through the necessary maintenance checks and upgrades.
"It is very important for the crews to start before Christmas, they have been with us for about 11 months and they are chomping at the bit to get started."
Mr Yeowart said passengers would initially be able to buy tickets on the train until its web-based ticket purchasing system was up and running.
The company is selling single journey tickets for £44 and £69 for return trips. First class fares are double.
The new service will call at Hartlepool, Eaglescliffe, Northallerton, Thirsk and York.
British Rail Class 43 number 43067 leads the first service into London King's Cross
Route of the new service.
Grand Central Railway have today launched a new train service between London King's Cross and Sunderland in the north east of England. The first service arrived in London shortly before 1030 UTC.

The company has been troubled with a variety of difficulties which have caused the launch to be cancelled on a number of occasions. More recently problems with acquiring rolling stock, the decision by the Office of Rail Regulation to allow the services was challenged by the then principal operator of East Coast Main Line services, GNER. 

The new service calls at Sunderland, Hartlepool, Eaglescliffe, Northallerton, Thirsk, York, and terminates at London King's Cross.

Grand Central are operating an interim timetable of one return journey per day until more rolling stock becomes available, expected by the end of January, to permit the full timetable of three return journeys to begin. 

The company is only one of a few "open access" operators in the United Kingdom which rather than bidding for a franchise and running a level of service set by government, Grand Central applied for access rights having identified a commercial opportunity.