In 1831 he was admitted to the École des Beaux-Arts de Lyon and a year later, he won the highest honor, the Golden Laurel.

After his return to Lyon in 1836, Janmot would attract the attention of critics of the Salon de Paris in conducting large-scale paintings with religious inspiration such as The Resurrection of the son of the widow of Nain (1839) or Christ in Gethsemane (1840).

Other orders followed, including the decoration of the dome of the Church of St. Francis de Sales and for the town hall that had been renovated by his friend the architect T. Desjardins.

Faced with family and increasing financial problems, Janmot came to Toulon, and despite some orders (new Portrait of Lacordaire (1878, Museum of Versailles), Rosaire (Saint-Germain-en-Laye, 1880), Martyrdom of St. Christine (Solliès-Pont, 1882), he lived a retired life.

He made charcoal drawings on the theme of the underworld, which can be regarded as a kind of continuation of the Poem of the Soul, including Purgatory (1885) and The End of Time (1888).

Janmot has been seen as a transitional figure between Romanticism and Symbolism, prefiguring the French part of the Pre-Raphaelite Brotherhood; his work was admired by Puvis de Chavannes, Odilon Redon, and Maurice Denis.