Warner and her sister, Anna, wrote a series of semi-religious novels that had extraordinary sales, including Say and Seal, Christmas Stocking, Books of Blessing (in 8 volumes), and The Law and the Testimony.

In 1849, seeing little change in their family's financial situation, Susan and Anna started writing to earn income.

In the nineteenth century, critics admired the depictions of rural American life in her early novels.

[2][3] Some of her works were written jointly with her younger sister Anna Bartlett Warner, who sometimes wrote under the pseudonym "Amy Lothrop".

After their conversion, they became confirmed members of the Mercer Street Presbyterian church, although in later life, Warner became drawn into Methodist circles.

Susan Warner died in Highland Falls, New York and is buried in the West Point Cemetery.