GATWICKExpress is increasing agents commission from 9% to 15% for bookings made over peak holiday periods.
The offer runs until January 8 to take in the winter half-term, Christmas and New Year holiday periods.
Some 1,800 agents with an Association of Train Operating Companies licence can take advantage of the promotion.
Market development manager Ian Jeffrey said: “At a time when the trend in the travel industry is to cut commissions, we are reaffirming our support for agents.”
He said Gatwick Express is also planning to increase its support for the trade by improving distribution opportunities. The trade generates £200m in revenue for rail firms each year.
The improved commission rate applies to single and return tickets from Victoria to Gatwick and for both club and standard class. The commission rise comes as the train operator invests £50m in new rolling stock and a new livery. Eight new trains have been ordered, with the first coming on track this winter.