Ryanair runs a Dublin service and will fly to Spain and Italy from the autumn - but that is likely to expand further.
Deputy UK Sales and Marketing manager Karl Hogstadius, who visited Doncaster this week, said: "The ambition is to continue to grow at all our destinations - and hopefully that will see more routes from Doncaster."
Ryanair staff were in the borough to promote their Ireland flights.
The company is also starting services to Girona, near Barcelona, and to Pisa in Italy later this year.
Mr Hogstadius said: "We're very happy with the development here in the region and the new airport.
"Dublin to Doncaster has been very successful so far and we're very happy about the passenger numbers.
"Already more than 100,000 passengers have flown on that route, and that is very good for what is still a new route. It means we have met out target for the first year. We're expanding with another two routes and that is another way of showing our confidence in the airport and the region.
"The ambition is to continue to grow at all our destinations, and hopefully that will see more routes from Doncaster."
He added the firm was now in negotiations with more airports from all over Europe.
But the destinations it serves from Doncaster will be limited because the firm will not run flights that take more than three hours, which could rule out some of its more distant routes such as Morocco.
The firm's flights between the Irish capital and South Yorkshire have not been one-way traffic out of Doncaster.
Although the majority of the passengers are heading off from the borough, the company's latest figures show 35 to 40 per cent have been travelling to Robin Hood airport as their destination.
Flights to Doncaster are advertised in Dublin - but not for the borough's tourist delights like Conisbrough Castle and its famous racecourse. Mr Hogstadius said the adverts simply state the name of the airport and the price of the flights.