Pre-tax profit fell £7 million (13.7%) from the £50 million posted during the six months to June 30, 2017.
Operating profit, meanwhile, slipped 14.3% to £63 million during the same period.
This was despite visitor numbers topping 30 million, up from 29.7 million during H1 last year.
Merlin said the results cover “seasonally quiet period”, with 70% of EBITDA typically generated during H2.
Adverse movements in foreign exchange and a weak dollar were the main factors affecting profit, said Merlin.
