The film was announced in May 2016, and much of the cast signed on a year later. Filming took place in Ayer, Massachusetts in June and July of 2017. Slender Man was released in the United States on August 10, 2018, by Screen Gems, and received a largely negative reception from critics and audiences alike, being called "boring" and "derivative".

Answer this question: when does slender man the movie come out? Let's give stream of consciousness first:
The relevant information is: Slender Man was released in the United States on August 10, 2018, by Screen Gems, and received a largely negative reception from critics and audiences alike, being called "boring" and "derivative".
So, the final answer is August 10 , 2018.