Merlin Entertainment said trade had been affected by “limited momentum” from The Lego Movie 2 as well as poor weather earlier this year.
The company said like-for-like sales for the first half of the year fell by 0.7% at Legoland.
But new Peppa Pig attractions abroad helped lift overall sales.
Merlin operates 127 attractions, 19 hotels and seven holiday villages in 27 countries.
The Lego Movie 2: The Second Part was released in February and has so far taken $191.3m at the box office.
However, Merlin Entertainment said that during the six months to 29 June, there has “been limited trading momentum as a result of the film itself”.
By comparison, the first Lego film took $469.1m and significantly boosted at sales at Merlin in 2014.
The firm, which also owns Alton Towers and Madame Tussauds, said sales for businesses open at least a year rose by 2.3% on improving tourist numbers in its key London market.
Total visitor numbers rose by 3% to 30.8 million.
Overall, pre-tax profits at Merlin Entertainment fell to £34m from £43m on sales 8.1% higher at £763m.