Ran was Kurosawa's last epic film and by far his most expensive. At the time, its budget of $12 million made it the most expensive Japanese film in history. Filming of Ran started in 1983. The 1,400 uniforms and suits of armor used for the extras were designed by costume designer Emi Wada and Kurosawa, and were handmade by master tailors over more than two years. The film also used 200 horses. Kurosawa loved filming in lush and expansive locations, and most of Ran was shot amidst the mountains and plains of Mount Aso, Japan's largest active volcano. Kurosawa was also granted permission to shoot at two of the country's most famous landmarks, the ancient castles at Kumamoto and Himeji. For the castle of Lady Sué's family, he used the ruins of the Azusa castle. Hidetora's third castle, which was burned to the ground, was actually a real building which Kurosawa built on the slopes of Mount Fuji. No miniatures were used for that segment, and Tatsuya Nakadai had to do the scene where Hidetora flees the castle in one take. Apparently, Kurosawa also wanted to include a scene that required an entire field to be sprayed gold; it was filmed but Kurosawa cut it out of the final film during editing. The filming of this scene can be seen in the documentary A.K..
Kurosawa would often shoot a scene with three cameras simultaneously, each using different lenses and angles. Many long-shots were employed throughout the film and very few close-ups. On several occasions he used static cameras and suddenly brought the action into frame, rather than using the camera to track the action. He also used jump cuts to progress certain scenes, changing the pace of the action for filmic effect.
Akira Kurosawa's wife of 39 years, Yōko Yaguchi, died during the production of this film. He halted filming for just one day to mourn before resuming work on the picture.
While most of the characters in Ran are portrayed by conventional acting techniques, two performances are reminiscent of Japanese Noh theater. The heavy, ghost-like makeup worn by Tatsuya Nakadai's character, Hidetora, resembles the emotive masks worn by traditional Noh performers. The body language exhibited by the same character is also typical of Noh theater: long periods of static motion and silence, followed by an abrupt, sometimes violent, change in stance. The character of Lady Kaede is also Noh-influenced. The Noh treatment emphasizes the ruthless, passionate, and single-minded natures of these two characters.
The description of Hidetora in the first script was originally based on Toshiro Mifune. However, the role was cast to Tatsuya Nakadai, an actor who had played several supporting characters in previous Kurosawa films, as well as Shingen and his "kagemusha", "double", in Kagemusha. Another Kurosawa veterans in Ran were Masayuki Yui (Tango), Jinpachi Nezu (Jiro) and Daisuke Ryu (Saburo), all of whom were in Kagemusha. Others had not, but would go on to work with Kurosawa again, such as Akira Terao (Taro) and Mieko Harada (Lady Kaede) in Dreams. Hisashi Igawa (Kurogane) would be in Rhapsody in August, and later, in Dreams, where Yui would also appear. Kurosawa also hired two comedians for lighter moments: Shinnosuke "Peter" Ikehata as Hidetora's fool Kyoami and Hitoshi Ueki as rival warlord Nobuhiro Fujimaki. Kurosawa hired approximately 1,400 extras.
Composer Toru Takemitsu originally wanted to use human voices as music for Ran. However, Kurosawa decided to have Takemitsu write a score influenced by the Austrian composer Gustav Mahler.
Kurosawa wanted the London Symphony Orchestra to perform the score for Ran. Upon meeting conductor Hiroyuki Iwaki of the Sapporo Symphony Orchestra, he engaged Iwaki and the orchestra to record the score. Kurosawa made the orchestra play up to 40 takes of the music.