Milena Smit was born on 5 October 1996 in Elche, Spain. She first started working in show business as a model when she was 15 years old. She worked in her home city and later moved to Madrid in search of career opportunities. Her father is Dutch.

She trained as an actress at the Cristina Rota acting school and was taught by Bernard Hiller, an acting coach of such actors as Leonardo DiCaprio and Cameron Diaz. Before becoming an actress, she was a waitress, shop assistant, babysitter, and information assistant on the subway.