Bertin was born on 2 July 1747. In 1770, at the age of 22, she opened her first boutique on the rue Saint-Honoré, called "Le Grand Mongol". Two years later, Bertin was introduced to Marie Antoinette. Following the coronation of Marie Antoinette's husband Louis XVI, Bertin began advising the Queen on fashion and clothing, becoming known as her "minister of fashion".
Bertin eventually diversified her stock to include bonnets, mantelets, pelisses, bows, and shirred veils. Amazed by this refinement, the Queen set about transforming Versailles' dress code with the help of Bertin. In order to allow women greater freedom of movement, dresses were simplified, in particular by abandoning panniers, which were considered too unwieldy. Bertin's success and popularity gave her customers from cities as far away as Koblenz, Brussels, London, and Saint Petersburg. Due to this diverse clientèle, Bertin managed to survive the French Revolution.
During this time, Bertin made costumes for the plays in the Café Théâtre, a club secretly owned by the Assassin Order. Despite her royal past, Bertin's shop was vandalized by Les Actes des Apôtres, a group of radical royalists. While Bertin attempted to take her costumes back, the royalists held her captive. The manager of the Café Théâtre, Charlotte Gouze, tasked her fellow Assassin Arno Dorian with finding her. Rescuing Bertin from her captors, Arno told her to flee while he recovered the costumes.