Higher wages and administration costs dragged pre-tax profits at independent tour company Paddywagon Tours down 40% to just under €740,000 last year.
Newly-filed accounts for the company, however, also show a 10% rise in revenue to €12.4m for the 12 months to the end of last October.
The sales rise was driven by the company attracting 250,000 tourists who visited sites like the Cliffs of Moher and Blarney Castle on its fleet of 60 recognisable green buses.
The company's workforce grew from 110 to 119 last year, with staff costs increasing from €2.8m to just over €3.1m. Paddywagon's accumulated profits stood at €3.4m at the end of its financial year, with its cash pile increasing marginally to €2.1m.
The company's founder Cathal O'Connell said last year's revenues were also boosted by an expansion of the firm's route network and "significant improvement" in its marketing.
He said passenger numbers are up by a further 15% to date in the current year.
Mr O'Connell said the company plans to bring in all-electric buses to do day tours within the Dublin area.
"There will be an immediate order of six electric buses in the new year increasing to 12 by the end of next year with the goal of having all of our buses electric in four years as technology improves," he said.