The photo sharing social media network - which is owned by Facebook - already requires users to be at least 13 years old, but now it is requesting more information to "keep young people safer".
In a blog post, the company said: "Asking for this information will help prevent underage people from joining Instagram, help us keep young people safer and enable more age-appropriate experiences overall.
"We will use the birthday information you share with us to create more tailored experiences, such as education around account controls and recommended privacy settings for young people."
According to Reuters, existing members won't be asked to provide their age as Instagram isn't sure if it would be too intrusive to ask.
Meanwhile, the social network also won't be verifying the date of birth information given by new users.
Child-protection charity NSPCC responded in a statement: "Asking users to provide an unverifiable date of birth will do nothing in practice to protect children from harmful or age-inappropriate content.
"Forthcoming regulation will force platforms to go further and will require them to take steps to proactively apply additional protections to children's accounts by default.
"But first and foremost the emphasis has to be on ensuring that platforms are safe in the first place for children to use."
Facebook added while it was aware "not everyone" will be honest about their age, they are looking into the best way to "verify" this detail, and insisted that is also a task for the wider industry.
The company said: "We understand not everyone will share their actual age.
"How best to collect and verify the age of people who use online services is something that the whole industry is exploring and we are committed to continuing to work with industry and governments to find the best solutions."