The film is directed by J.A. Bayona who was inevitable praised for his previous directing work The Orphanage.

The critics site Rotten Tomatoes reports an approval rating of 85% for the film, based on 52 reviews, with an average rating of 7.4/10. The site reads, "A Monster Calls deftly balances dark themes and fantastical elements to deliver an engrossing and uncommonly moving entry in the crowded coming-of-age genre".

The intriguing Score for the film is composed by Fernando Velázquez, who already had experience in the world of cinema and especially in the terror genre. He composed films like Devil, written & produced by M. Night Shyamalan, and the Guillermo del Toro produced feature The Orphanage.

In 2010 he was one of eleven selected composers to create symphonic works for the Bilbao Symphony Orchestra. In the same year Film Music Magazine rated his score to 'Devil' as one of the best scores of the year, quoting "Velazquez's brassily orchestral ambitions pay more of a blood oath to Bernard Herrmann and James Newton Howard, with the kind of churning, melodically rich symphonic sound that makes DEVIL's mostly elevator-bound setting anything but claustrophobic".

Two years later Film Music Magazine ranked his score to 'The Impossible' as one of the Top 10 scores of the year.