Maku was the captain of Amajita when they lifted the COSAFA Cup trophy in Mozambique earlier this year under the head coach Raymond Mdaka.
The teenage midfielder started out at the Ubuntu Academy in Cape Town before getting a big move to SuperSport United.
Maku joins a start-studded Sundowns squad that have already won the MTN8 trophy this campaign, while also competing on multiple fronts that includes being one of the favourites in the CAF Champions League.
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The Tshwane club wrote on social media: “Mamelodi Sundowns are pleased to announce the signing of Lazola Maku! Yellow Nation, let’s give the youngster a proper welcome.”