Debra Caplin will start work as head of the Bnos Beis Yaakov School in Kingsbury from the new term.
The governors believe Mrs Caplin - who has varied Jewish school teaching and management experience - will further the development of the girls' school, opened two years ago to cater for demand from the Charedi community.
From the next academic year, the school will have 70 pupils in four classes, from nursery to year two, at its Kingsbury Synagogue premises. Many of the girls are from families new to the area. Its founders include educational philanthropist Benjamin Perl, who is its honorary president.
The governors are "delighted that someone as experienced and professional as Mrs Caplin has agreed to lead the school into the future".