Variety says: "Though the theme of childhood innocence remains at the core of It: Welcome to Derry, the show expands even further to address the issues that continually haunt the essence of the American experience. Abuse, racism, psychological trauma, infringement on Indigenous land and militarization are all significant elements here. When it's all said and done, It: Welcome to Derry is a worthy prequel series that not only details the emergence of Pennywise, but also turns a lens on society to showcase how truly horrifying we can be as human beings."

IndieWire gave it a C-, writing: "What works about the movies -- the believable kid behaviors, Skarsgård's performance, and a steady stream of scares -- isn't what's driving the show. Episodes strain to touch on those fan-favorite aspects almost as often as they work to expand the Stephen King universe from within (even incorporating a missing kid plot reminiscent of It: Chapter One). But an engine fueled by filling in the blanks isn't built to last, and these dots, once connected, prove tacky and sour (especially without Pennywise, who's notably absent for most of the season)."

IGN says: "IT: Welcome to Derry's premiere makes you feel right at home in America's worst small town. The first episode accomplishes its most important task of re-establishing Derry and Pennywise with style and some expertly-drawn out tension, though some of the more CG-heavy scares fall flat. Indirectly honoring a popular critique of the novel, the kids' side of the story is (so far) way more compelling than the adults', but Pennywise has barely begun to poke his red-tufted head out of the sewer, so there's plenty of time for that storyline to start floating. We all float down here, after all."

The Wrap says: "Yes, It the book came out well before Stranger Things appeared, as did the beloved 1990 miniseries that no doubt inspired the Duffers. But Welcome to Derry feels like a lesser imitation of the Netflix phenomenon in almost every way. Things mythology and monsters are cooler, the characters are generally richer with more complex psychology, and the evocation of smalltown 1980s isn't as hamfisted (nor anachronistic) as this show's early '60s."

Collider says: "IT: Welcome to Derry should satisfy die-hard King fans who have been yearning for an extended universe, with references to the Bower Gang and a focus on the Indigenous origins of the titular entity. As a horror show, however, it pales in comparison to what Muschietti was able to do with his movie adaptations. Perhaps if I were less of a fan of the films or the book that started it all, I would have had a better time with this, but that same, deep-rooted horror never fully took hold. Thanks mainly to the performances of Paige, Adepo, and Chalk, IT: Welcome to Derry is not without its storytelling merits, even if none of them are all that scary."