Mongez started studying under Jean-Baptiste Regnault in the early 1790s and then, after mastering the basics, she became a pupil of Jacques-Louis David, who at the time was one of the leaders of the Neoclassical movement in France.

On 9 June, 1792, accompanied by Bon-Joseph Dacier, his colleague at the academy, Lacepede and the Abbe Sieyes, Mongez and Angelique were married in a civil ceremony.

Mongez established herself as a Neoclassical history painter from the outset of her career, boldly disregarding criticisms related to her gender.

Until her passing, Mongez's dedication to Davidian painting was evident in her diverse body of work, ranging from engravings to framed drawings, portraits, busts, and beyond.

Mongez’ principle works include her first major painting, Astyanax Snatched from His Mother (1802), Alexander Weeping Over the Death of the Wife of Darius I (1804), Theseus and Pirithous (1806), Orpheus in Hell (1808), The Death of Adonis (1810), Perseus and Andromeda (1812), Mars and Venus (1814), Saint Martin Sharing his Cloak with a Beggar (1819), and her last Salon exhibit The Seven Against Thebes (1827).

Her paintings contained more dynamic compositions and female nudity, something that her male contemporaries were prohibited from depicting within the confines of the Prix de Rome.

Despite this, she received state encouragement and radical class support, as well as patronage from the Russian Prince Youssoupov and Louis XVIII, whose portrait she painted after the Bourbon Restoration.

For Le Journal des Arts, the painting was one of the finest works of the modern school; yet other critics attributed the most beautiful parts to David.

At the next Salon (1804), Angelique Mongez exhibited another great figure of history: Alexander Weeping Over the Death of the Wife of Darius I, for which she received a gold medal.

In 1827, the critic Étienne-Jean Delécluze wrote of her The Seven Against Thebes (now in Musée des Beaux-Arts d'Angers): "Madame Mongez imitated David.

Stéphanie Dermoncourt of the Museum of Fine Arts of Lyon says that her figure of Polystratus carrying water to Darius is very similar to the Oedipus of Ingres.