The requirements apply to providers with at least eight million users in the Southeast Asian country -- including Facebook, Instagram, TikTok and YouTube.
But platforms will be given a grace period to implement the measures, the communications regulator has said, without specifying its duration.
The country is the latest to attempt to restrict young people's access to social media platforms, as concern grows worldwide over their negative impact on child wellbeing.
From Monday, "users below the age of 16 are not permitted to register for social media accounts", according to an FAQ document released by the Malaysian Communications and Multimedia Commission (MCMC) before the new rules came in.
Platforms are expected to implement "age verification measures", the FAQ said, including checks against government-issued records such as identity cards or passports.
