The Australian actress, 55, dressed to impress in a long white frock and black coat as she left the Khaite fashion show with the teenager.
The Hollywood star completed her stylish look with a pair of black gloves and black shoes.
Naomi left her short blonde locks out and showed off her flawless complexion with a natural makeup palette.
She was joined by Kai, 15, who wore a long brown dress and a leather jacket with fur collar while posing alongside the actress.
Naomi Watts looked stylish as she attended New York Fashion Week with her youngest child Kai on Saturday
Naomi shares her two children (Alexander, 16, and Samuel – who prefers the name Kai, 15) with her ex-partner Liev Schreiber who she split with in 2016 after 11 years.
Despite her breakup from ex-partner Liev, the former couple have remained on friendly terms and are committed to co-parenting their two children.
Naomi shared news of her marriage with her followers as she took to Instagram posting a photo of herself and her new husband as she posed on the steps of Manhattan courthouse shortly after tying the knot.
The British-Australian actress stunned in a $7,400 white Oscar de la Renta Sweetheart Water Lilly Guipure dress as she captioned the post: ‘Hitched.’
Naomi first sparked rumours that she and Billy were engaged earlier in the year when she debuted an enormous diamond with a marquise cut along with a diamond-encrusted band.
The Australian actress, 55, dressed to impress in a long white dress and black coat as she left the Khaite fashion show with the teenager
Naomi is pictured with her ex-partner Liev Schreiber and their children Sasha and Kai in 2015
The star however refused to confirm the engagement chatter, even after American Today show host Hoda Kotb directly referenced it during a late April appearance on the morning talk show.
Toward the end of Naomi’s segment, Hoda joked that her ‘eye was hurting’ from the ‘big glint coming from some ring over here.’
Naomi and Billy met on the set of her 2017 Netflix series Gypsy, in which she starred as a therapist who uses an alias to develop close (and unethical) relationships with people intimately connected to her patients, while Crudup played her husband.
The costars began a relationship later in 2017, a year after Naomi had split from her partner of 11 years, the actor Liev Schreiber.
Naomi shares her two children (Alexander, 16, and Samuel – who prefers the name Kai, 15) with her ex-partner Liev Schreiber who she split with in 2016 after 11 years