After the death of Bourdonnais in 1840, Saint-Amant had the reputation of being France's best chess player, but he was not nearly as strong as his predecessor Bourdonnais. He first was the secretary to the governor of French Guiana, until he protested against the slave trade. After that, he tried his hands as an actor, then became a successful wine merchant and was a captain in the National Guard during 1848 revolution. In 1851, he became a consul to California eight years after the Englishman Howard Staunton bested him. He played two matches against the Howard Staunton in 1843. The first, in London, he won 3½-2½, but a return match just before Christmas in Paris, he lost 13-8. This second match is sometimes considered to be an unofficial World Chess Championship match.
Saint-Amant was in Paris in 1858 when Paul Morphy made his first visit. The Frenchman freely admitted that he was not in Morphy's class as a chess player, and was present at a banquet honoring the young American. They did play a few games privately. Only the score of one game is known, a win by Morphy.
In 1861 Saint-Amant moved to Algeria to spend his retirement years. He died there in 1872 after an accident.