[1] In 1888, The Atlantic Monthly described him as "a portraitist of talent",[2] adding that Stuart is quoted as having said of one of Frothingham's head portraits, "No man in Boston but myself can paint so good a head," and that Frothingham was greatly helped by Stuart's criticisms and encouragement, although initially his Nestor had advised him to adopt another, less precarious means of earning a livelihood.

[2] The Atlantic noted that there is a detailed portrait of Samuel Dexter by Frothingham in the Harvard Memorial Hall, in which Dexter, wearing a white wig and a red cloak atop a black coat, holds a book in his hand, and appears lost in meditation, saying the flesh coloring in the painting is rather dry and parchment-like, but overall, the color is harmonious.

Dunlap noted that heads depicted by James Frothingham were painted with great truth, freedom, and excellence.

[2] He painted a number of likenesses in Salem, Massachusetts, including the wealthy merchant Elias Hasket Derby.

Frothingham would have been a regional competitor to the younger Chester Harding (1792–1866), but moved to Brooklyn in New York City in 1826.