In the first instalment of her new video blog for E!, she took viewers on a tour of the toddler's closet.
The impressive array includes jackets from Ralph Lauren and H&M, piles of cardigans and sweaters, and a whole counter dedicated to accessories like trilby hats and bow ties.
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Future fashionista: Kourtney Kardashian reveals 23-month-old son Mason's impressive array of clothes with a tour of his closet on her new video blog
The 32-year-old, who announced this week that she is nine weeks' pregnant with her second child, also doled out some child styling advice to fellow mothers.
Fancy footwear: The toddler has gold Supra hi-tops (left) and suede moccasins in every colour (right)
Expensive taste: Kourtney loves a denim jacket on her son - especially this Ralph Lauren number
Shoes, in particular, are one way to do this, she says.
'I think with boys… it’s all about shoes,' she tells viewers. 'I've seen so many little boys and their outfits are so cute and then their moms put kind of dorky shoes on them.'
Indeed, young Mason's extensive footwear collection is far from 'dorky'.
Accessorize all areas: Mason has several pairs of sunglasses (left) and even tiny bow-ties (right)
The accessory obsession doesn't end there. Mason has sunglasses in multiple colours, including hot pink, and bow-ties, which Kourtney says she teams with button-down shirts.
He even has his own mini trilby, which his mother says is 'a fun way to instantly add style'.
An outfit for every occasion: The closet is packed with shirts and jackets in every possible print and fabric
More clothes than Mommy? As well as the closet, Mason needs a dresser for his piles of knitwear
She names H&M as one of her favourite places to find well-priced, trend-led pieces, because, as she points out, 'kids definitely grow out of their clothes really quickly.'
Instead, she whispers, 'let the grandmas buy the expensive stuff.'