Production notes

After setting up his animation studio in Madrid, Spain, director Sergio Pablos, who had worked on Disney Renaissance films such as The Hunchback of Notre Dame, Hercules, and Tarzan, decided to develop a new traditionally-animated feature film. Pablos wanted to explore how the medium would have evolved had western animation film studios not switched to producing mostly computer animated films since the 1990s. For the film's look, the studio sought to overcome some of the technical limitations that traditional animation had, focusing on organic and volumetric lighting and texturing to give the film a unique look, while maintaining a hand-crafted feel. Proprietary tools from Les films du Poisson Rouge, a French company in Angoulême, were used to allow the team to produce a variety of visual development styles, with the aim of getting away from the standardized style of "characters looking like stickers put on painted backgrounds." Fellow Disney animators James Baxter, known for Beauty and the Beast, and Andrew Chesworth also worked on the film. The first teaser for the project was released in April 2012; at the time, the studio was seeking investment, co-production, and distribution partners. It was shopped around to various studios, but most studios — including Netflix at first — rejected the movie viewing it as "too risky." In November 2017, Netflix announced that they had acquired the global rights to Klaus; at the same time, the casting of Schwartzman, Jones, Simmons, and Cusack was announced along with a Christmas 2019 release date. In March 2019, it was reported that Netflix was planning an Oscar-qualifying run for Klaus in theaters, and it was listed as one of ten films Netflix was negotiating with chains to give limited releases prior to their online debuts that August. The film is dedicated to animator and scene checker Mary Lescher who died on 2 June 2019 of cancer. She had worked on Klaus, as well at both Disney Animation and DisneyToon Studios from 1989 to 2006. Pablos said Smeerensburg is a deliberate misspelling of Smeerenburg, a former Dutch and Norwegian whaling station in the Arctic archipelago of Svalbard.

Pablos said the story was indirectly inspired by the Christopher Nolan film Batman Begins. "What a great storytelling exercise, to take a character that's already well established … and bring it to today's audience". Pablos workshopped origin story retellings for several characters, including real-life figures like Napoleon Bonaparte and magical figures including Dracula before settling on Santa Claus. "He has many origin stories, but in the end I thought that there was not one canon-accepted origin story," according to Pablos, whose travels to Norway inspired much of the direction of the film, including the inclusion of the Sami people. It was this decision that led to Netflix green-lighting the project, as the streaming giant had not been interested in original feature-length animation but made an exception due to an interest in releasing new Christmas stories.

On review aggregation website Rotten Tomatoes, the film has an approval rating of 95% based on 78 reviews with an average rating of 7.7/10. The critical consensus reads "Beautiful hand-drawn animation and a humorous, heartwarming narrative make Klaus an instant candidate for holiday classic status." On Metacritic the film has a weighted average score of 65 out of 100, based on 13 critics, indicating "generally favorable" reviews. John DeFore of The Hollywood Reporter gave the film a positive review, writing: "Sergio Pablos' Klaus invents its own unexpected and very enjoyable origin story for the big guy who gives out toys every Christmas eve. Shaking off most Yuletide cliches in favor of a from-scratch story about how even dubiously-motivated generosity can lead to joy, it contains echoes of other seasonal favorites (especially, in a topsy-turvy way, Dr. Seuss' Grinch) while standing completely on its own." Peter Debruge of Variety gave the film a mixed review, calling the film over-complicated and saying: "What goodwill the movie does inspire owes more to the splendid visual world than to anything the story supplies." According to data provided by Netflix to Reuters, the film racked up nearly 30 million views worldwide in its first month. The film beat Toy Story 4 for Best Animated Film of 2019 on Animation Magazine. Deseret News named Klaus on their list of underrated Christmas movies to watch in 2023.