Akira Kurosawa had originally wanted to direct a film about a single day in the life of a samurai. Later, in the course of his research, he discovered a story about samurai defending farmers. According to actor Toshiro Mifune, the film was originally going to be called Six Samurai, with Mifune playing the role of Kyuzo. During the six-week scriptwriting process, Kurosawa and his screenwriters realized that "six sober samurai were a bore—they needed a character that was more off-the-wall". Kurosawa recast Mifune as Kikuchiyo and gave him creative license to improvise actions in his performance.
The film took a year to complete. It had become a topic of wide discussion long before it was released. After three months of pre-production the film had 148 shooting days spread out over a year—four times the span covered in the original budget, which eventually came to almost half a million dollars. Toho Studios closed down production at least twice. Each time, Kurosawa calmly went fishing, reasoning that the studio had already heavily invested in the production and would allow him to complete the picture. The film's final battle scene, originally scheduled to be shot at the end of summer, was shot in February in near-freezing temperatures. Mifune later recalled that he had never been so cold in his life.
Kurosawa and the writers were innovative in refining the theme of the assembly of heroic characters to perform a mission. According to Michael Jeck's DVD commentary, Seven Samurai was among the first films to use the now-common plot element of the recruiting and gathering of heroes into a team to accomplish a specific goal, a device used in later films such as The Guns of Navarone, Sholay, the western remake The Magnificent Seven, and Pixar's animated film A Bug's Life. Film critic Roger Ebert speculates in his review that the sequence introducing the leader Kambei (in which the samurai shaves off his topknot, a sign of honor among samurai, in order to pose as a monk to rescue a boy from a kidnapper) could be the origin of the practice, now common in action movies, of introducing the main hero with an undertaking unrelated to the main plot. Other plot devices such as the reluctant hero, romance between a local woman and the youngest hero, and the nervousness of the common citizenry had appeared in other films before this but were combined in this film.
Kurosawa refused to shoot the peasant village at Toho Studios and had a complete set constructed at Tagata on the Izu Peninsula, Shizuoka. Although the studio protested the increased production costs, Kurosawa was adamant that "the quality of the set influences the quality of the actors' performances... For this reason, I have the sets made exactly like the real thing. It restricts the shooting but encourages that feeling of authenticity." He also spoke of 'intense labour' of making the film: "It rained all the time, we didn't have enough horses. It was just the kind of picture that is impossible to make in this country."
Through the creative freedom provided by the studio, Kurosawa made use of telephoto lenses, which were rare in 1954, as well as multiple cameras which allowed the action to fill the screen and place the audience right in the middle of it. "If I had filmed it in the traditional shot-by-shot method, there was no guarantee that any action could be repeated in exactly the same way twice." He found it to be very effective and he later used it in movies that were less action-oriented. His method was to put one camera in the most orthodox shooting position, another camera for quick shots and a third camera "as a kind of guerilla unit". This method made for very complicated shoots, for which Kurosawa choreographed the movement of all three cameras by using diagrams.
The martial arts choreography for the film was led by Yoshio Sugino of the Tenshin Shōden Katori Shintō-ryū. Initially Junzo Sasamori of the Ono-ha Itto-ryu was working along with Sugino, but he was asked by the Ministry of Education to teach in Europe during production.
Following the filming, Kurosawa quickly earned a reputation with his crew as the "world's greatest editor" because of his practice of editing late at night during the shooting. He described this as a practical necessity that is incomprehensible to most directors, who on major production spent at least several months with their editors assembling and cutting the film after shooting is completed.:89