Early in 2021, there were rumours that Lokesh Kanagaraj and Vijay would work together again on a second movie together after Master (2021),[10] following Lokesh's commitments to Vikram (2022),[11] while Vijay would work with Nelson on Beast (2022) before signing Vamshi Paidipally's project, which would later be known as Varisu (2023).[12] Lokesh said that talks were on for him to helm Vijay's 67th movie in March 2022.[13] He announced the idea in May of that year, with the working title Thalapathy 67.[14]
The funding for the project came from S. S. Lalit Kumar's Seven Screen Studio, which also distributed and co-produced the Vijay movie Master[15]. Jagadish, Vijay's manager, is also a co-producer. The project was confirmed by the corporation on January 30, 2023,[16][17], and Leo was announced as the movie's official title on February 3, 2023
.Writing and pre-production took Lokesh close to six months.In his third consecutive cooperation with the director, Lokesh and Rathna Kumar co-wrote the script for the movie. [24]Deeraj Vaidy, who directed the 2016 film Jil Jung Juk, also joined the writing team [26].[27] Unlike Master, which he deemed to be a 50% Vijay film and 50% his film, Lokesh promised that the movie will be entirely produced in his way.[24] The cast and crew of the movie attended a muhurat puja on December 5, 2022, at AVM Studios in Chennai.[28] On December 7, the crew spent nearly three days filming the movie's promotional video.[29]
Manoj Paramahamsa's appointment as cinematographer was revealed in mid-January 2023, marking his first collaboration with Lokesh and third with Vijay following Nanban (2012)
After 30 possible hairstyles, Vijay's character will wear a grey-shaded hairdo, which was ultimately chosen.[36]After appearing with Vijay in Ghilli (2004), Thirupaachi (2005), Aathi (2006), and Kuruvi (2008), Trisha was chosen as the female lead.[39][40] Sanjay Dutt, a Bollywood actor, has officially been cast as one of the film's key adversaries in both his debut Tamil film and his follow-up South Indian film to K.G.F: Chapter 2 (2022).[41] Dutt decided to work on the project after being struck by the film's one-line narration.Along with Priya Anand, who had a significant role in the movie, Arjun was also cast in a significant role.[44] He described it as one that would support his claim to the moniker "action king" and be "different" and "fresh".[45]
On January 2, 2023, at Chennai's EVP Film City, the first schedule of principal photography got underway.[58] In the final week of January, a few minor filming locations were used in Kodaikanal.[59] Kashmir saw the start of the second schedule on February 1.[60] The film's official technology security partner issued a warning to the public during this time frame when footage of Vijay was released and quickly went viral[61]. They advised people not to share the information since it would be removed.[62] In order to avoid the leak of photos and films from the production, the majority of the cast and crew were also forbidden from using mobile devices on the sets.[63] Mysskin tweeted on February 27, 2023, that the filming of his scenes, which featured a challenging stunt sequence, was complete.[64][65] Early in March, Menon declared
