Highlands and Islands Airports Limited (Hial) said a total of 1,451,793 passengers passed through it 11 sites, a 3.2% rise on the previous year.
Inverness was the busiest airport in the group thanks to its connections to Amsterdam, Dublin, Geneva and Zurich.
Dundee, Islay, Barra, Benbecula and Tiree also had increased passenger figures, but they fell at other sites.
These included Sumburgh, Kirkwall, Campbeltown, Wick John O'Groats and Stornoway.
Figures for the last quarter of 2015 - October-December - also showed that passenger numbers fell across the group.
Hial said that this was largely as a result of the loss of services between Inverness and London City and bad weather and cancellations affecting flights.
There was also less demand from the energy sector, including the North Sea oil and gas industry.
Inglis Lyon, managing director of Hial, said: "The last 12 months have been the busiest in HIAL's 30 year history with record numbers of business and leisure passengers using our airports.
"This growth illustrates the enormous importance of our regional airports to Scotland's economy."
He added: "We will continue to invest in our airports, with major developments planned or underway at Inverness and Sumburgh this year, and continued efforts to improve our customer service and attract more business across the group.
"Notwithstanding the welcome arrival of British Airways and KLM at Inverness we have more work to do to attract new business and improve our financial outlook."
Scotland's regional airports group has said 2015 was its busiest year yet in its 30-year history.