IOC sports director Kit McConnell said the Tokyo Games would include 321 events, up from 306 at Rio 2016, with a focus on redressing the Olympic movement's long-standing disparity between male and female athletes.
Appealing to a more "urban" audience was another priority, he told reporters, announcing that both male and female 3-on-3 basketball and BMX freestyle had been added to the lineup.
Aside from the track relay, Tokyo will also see new mixed swimming events, including a 4x100 medley relay, along with mixed events in archery, judo and cycling.
"We have taken a really important step forward in terms of gender equality," McConnell said, with the IOC having already laid out a goal of a 50-50 gender split among Olympians.
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IOC chief Thomas Bach added in a statement that the "new events that we approved today, together with the five new sports that were added to the Tokyo 2020 programme last year, represent a step-change in the Olympic programme."
The Olympics governing body also highlighted that while boosting female participation and, in theory, youth appeal, Tokyo 2020 will still have a lighter "footprint" than Rio 2016.
Despite an increase in events, there will be an overall reduction of 285 in the number of athletes.
The IOC said the process of changing the Summer Games programme began after Rio, when sports federations were able to review data on the appeal of their sports and specific events, before requesting changes for Tokyo.
"We had a large number of requests from international federations," McConnell said. "It is not possible to meet every request with a positive answer."