The total, which represents an 11.3% rise on the 2014 figures reported by newly created operator Lithuania Airports, is significantly higher than the country's estimated population of 2.9 million people.
Lithuania Airports reveals that all three gateways reported growth, with Vilnius handling more than 3mppa for the first time in its history.
Its final figure for 2015 was 3.3 million – an increase of 13.4% on the 2.9 million passengers to use its facilities in 2014.
Palanga and Kaunas in comparison handled 145,000 and 747,000 passengers in 2015 – growth of 9.4% and 3.2% respectively on the previous year.
The most popular destinations in Vilnius and Palanga remained the same in 2015 – flights to London, Frankfurt and Riga receive most passengers in the capital, while Copenhagen remains the leader in Palanga.
Holiday destinations were especially demanded in Kaunas in 2014, but in 2015 they were pushed from the top of the most popular list by London, Dublin and Copenhagen.
“The number of people travelling by air and using airport services has been growing steadily since 2009," says Gediminas Almantas, CEO of Lithuanian Airports.
"Vilnius alone showed the growth in the number of passengers by 2.5 times in six years.
"The mobility of the country’s population keeps growing – both for tourism and business purposes. Further, Lithuania is increasingly spotted in the international arena and is frequented by visitors from abroad.
"Next year, with new carriers and new destinations, we will expand the opportunities for travellers even more, therefore we expect that this growth will not stop."