IGTV lets users create content exceeding the current maximum 60-second clip limit for the first time.
It's not clear if the longer videos would include adverts or if users would be paid for their content as they are on platforms like YouTube.
Speaking exclusively to Newsbeat, Instagram founder Kevin Systrom said it's in "no rush to figure that out".
IGTV will show videos in portrait mode, which Instagram says is the "natural way" people use their phones.
Kevin said: "Video deserves a better home on mobile".
Tech expert Alex Brinnand, from TenEighty magazine, says IGTV could make Instagram a more dominant player in the social media industry.
He said: "We're still yet to see exactly what power Instagram does have. I'm sure there are lots of discussions happening at other platforms about how much of a threat this could be and those are valid".
The longest video you can currently post is 60 seconds long - that's in "feed" mode - the main bit of Instagram you see when you open the app.
Instagram Stories - which normally expire after 24 hours - have a 15-second video limit per clip.
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