Sarah was born in Montreal, Canada. After graduating with an honors degree in English literature from McGill University, she moved to Toronto to work for Harlequin Enterprises. While she never met Fabio, she used her romance publishing experiences to fuel her first novel Milkrun.
Since then, Sarah has written four additional novels for adults: Fishbowl, As Seen on TV, Monkey Business, and Me vs. Me; the New York Times bestselling middle grade series Whatever After; the middle grade series Upside-Down Magic (with Lauren Myracle and Emily Jenkins); and the teen novels Bras & Broomsticks, Frogs & French Kisses, Spells & Sleeping Bags, and Parties & Potions (all in the Magic in Manhattan series), as well as Gimme a Call, Ten Things We Did (And Probably Shouldn't Have), Don't Even Think About It, Think Twice, and I See London, I See France. Along with Lauren Myracle and E. Lockhart, Sarah also wrote How to Be Bad, and along with Farrin Jacobs, she wrote See Jane Write, a guide to writing. Sarah also co-edited two bestselling charity collections (Girls' Night In and Girls' Night Out), and has contributed to various anthologies (American Girls About Town, Sixteen: Stories About That Sweet and Bitter Birthday, 21 Proms, First Kiss (Then Tell), Fireworks, and Vacations from Hell).
Sarah is also a co-founder of OMG BookFest, a celebration of books aimed at the early to middle grade reader (ages 7-12) that brings together commercial and award-winning authors with underserved local communities for an exciting experience of books, games and activities.
Sarah's books have been translated into twenty-nine languages and optioned to Hollywood. She now lives in New York City with her husband and two daughters.