Militants attacked the upscale cafe in the Bangladeshi capital, killing 20 foreigners inside, before police stormed the building on Saturday and rescued 13 hostages.
Military officials said all of those killed were foreign, and that the dead included Japanese and Italian nationals.
The attack, claimed by IS, marks a major escalation in a campaign by the group over the past 18 months that had targeted mostly individuals advocating a secular or liberal approach in mostly Muslim Bangladesh.
Prime Minister Sheikh Hasina said in a TV broadcast that six gunmen were killed during the police operation and one was captured.
The army concluded an operation to clear the cafe after a 12-hour siege that began when gunmen stormed the restaurant on Friday night. Two police officers were killed in the initial assault.
An army spokesman said the 13 hostages that were rescued included one Japanese and two Sri Lankans.
A Japanese government spokesman said one Japanese man was among those rescued and taken to a Dhaka hospital with a gunshot wound. Seven Japanese were unaccounted for.
Italy's ambassador to Bangladesh, Mario Palma, told Italian state TV seven Italians were among the hostages.
IS posted photos of what it said were dead foreigners killed in the assault, which could deal a major blow to the country's vital $25 billion garment sector.