The group released a trading update for the 40 weeks ended October 6, including the key summer trading period of July and August, on Tuesday, October 17.
It reported 4.7% group organic revenue growth year to date, driven primarily by new business development.
Resort theme parks saw organic revenue growth of 9%, with particularly strong like for like trading.
Midway Attractions – including Madame Tussauds and Sea Life – saw organic revenue growth remain flat.
Nick Varney, Merlin Entertainments chief executive, said: "Group trading has been in line with expectations, with variances by operating group reflecting the diversified nature of the portfolio.
“We have opened a record 644 rooms, and six new Midway attractions which has resulted in organic revenue growth of 4.7%. Continued strong guest demand for our themed accommodation offering and the ongoing trend towards short breaks has driven 27.7% growth in accommodation revenue.
“The impact of terror attacks which adversely affected performance from early 2017 has started to abate and we have seen early signs of recovery in the London tourism market over the summer.
“We are excited by the recent launch of our two new Midway brands – The Bear Grylls Adventure in Birmingham, UK, and Peppa Pig World of Play in Shanghai.
“It is too early to comment on their commercial success, which as for all new brands could take time to build, but the attractions look fantastic and we are pleased with early guest feedback.
“The cost environment remains challenging, with tighter labour markets in many parts of the world adding to the pressures resulting from legislative changes such as the National Living Wage in the UK."