The decision was made less than three weeks before the world-leading social media ban comes into effect on December 10.
"(Twitch) has the sole or significant purpose of online social interaction with features designed to encourage user interaction, including through live streaming content," the commission said in a statement.
"Twitch is a platform most commonly used for live streaming or posting content that enables users, including Australian children, to interact with others in relation to the content posted."
The platform will join other sites including TikTok, Instagram, YouTube and Facebook which will be off limits for children under 16.
Social media sites caught up in the ban will have to take reasonable steps to keep young users off them, or face fines of up to $49.5 million.
The eSafety Commission said Pinterest would not be included in the list of platforms subject to the age restrictions.
"While Pinterest enables some online social interaction, it is not the significant purpose. Pinterest is more commonly used by individuals collating images for inspiration and idea curation," the commission said.
The commission said no further assessments of other social media sites were planned in the lead up to the ban coming into effect.
"eSafety has been assessing platforms against the criteria set out in the social media minimum age legislation and the minister for communications' legislative rules over recent months," the commission said.
The federal government has previously said the list of platforms ion the social media ban was fluid, with the prospect of more being added.
Popular gaming platform Roblox has remained exempt from the ban, despite calls for it to be included in the list.
On Thursday, Meta announced it would begin removing access to its platforms for users under 16 as early as December 4.
Meta said users would receive a two-week notice period through a combination of in-app messages, emails and text messages before they lose access to their accounts.
25°C