The 12-year-old child star, who plays Eleven in the hit Netflix show, was recently unveiled as the face of Calvin Klein's new campaign, and now she has a major agency behind her.
IMG agents also represent Hadid sisters Bella and Gigi.
Uploading one of the images from her new CK campaign to her Instagram account, Millie recently told her 2.5 million followers she was "so honoured to be a part of this".
"A cast of distinct individuals brings the idea to life: Strength of character is key. Whether famous or unknown, all are treated equally" - Calvin Klein By Appointment," she added in the caption.
Models Natalie Westling, Abbey Lee Kershaw, and Kiki Willems also star in the campaign.