Much of Kaurismäki's work is centred on Helsinki, such as the film Calamari Union, the Proletariat trilogy (Shadows in Paradise, Ariel and The Match Factory Girl) and the Finland trilogy (Drifting Clouds, The Man Without a Past and Lights in the Dusk). His vision of Helsinki is critical and singularly unromantic. Indeed, his characters often speak about how they wish to get away from Helsinki. Some end up in Mexico (Ariel), others in Estonia (Shadows in Paradise, Calamari Union, and Take Care of Your Scarf, Tatjana). The setting of most of his films is the 1980s, or at least contains elements from that decade.

After graduating in media studies from the University of Tampere, Aki Kaurismäki started his career as a co-screenwriter and actor in films made by his older brother, Mika Kaurismäki. He played the main role in Mika's film The Liar (1981). Together they founded the production company Villealfa Filmproductions and later the Midnight Sun Film Festival. His debut as an independent Director was Crime and Punishment (1983), an adaptation of Dostoyevsky's novel set in modern Helsinki. He gained worldwide attention with Leningrad Cowboys Go America (1989). In 1989 he emigrated with his wife to Portugal, saying "in all of Helsinki there is no place left where I could place my camera".

Kaurismäki's film Ariel (1988) was entered into the 16th Moscow International Film Festival where it won the Prix FIPRESCI.

Kaurismäki's most acclaimed film has been The Man Without a Past, which won the Grand Prix and the Prize of the Ecumenical Jury at the 2002 Cannes Film Festival and was nominated for an Academy Award in the Best Foreign Language Film category in 2003. However, Kaurismäki refused to attend the Oscar ceremony, asserting that he did not feel like partying in a country that was in a state of war. Kaurismäki's next film Lights in the Dusk was also chosen to be Finland's nominee for best foreign-language film, but Kaurismäki again boycotted the awards and refused the nomination, in what he claimed was a protest against U.S. President George W. Bush's foreign policy. In 2002 Kaurismäki also boycotted the 40th New York Film Festival in a show of solidarity with the Iranian Director Abbas Kiarostami, who was not given a US visa in time for the festival.

Kaurismäki has been a vocal critic of digital cinematography, calling it "a devil's invention" and saying he "won't make a digital film in this life". In March 2014, however, he reconciled, saying that "in order to maintain my humble film oeuvre accessible to a potential audience, I have ended up in rendering it to digital in all its present and several of its as yet unknown forms."

Kaurismäki's 2017 film The Other Side of Hope won the Silver Bear for Best Director award at the 67th Berlin International Film Festival. At the same festival he also announced that it would be his last film as a Director.