He studied with Lorens Pasch the Younger and Louis Masreliez at the Royal Swedish Academy of Arts.

He served as Director there from 1828 to 1840 and, in 1843, was appointed a "Hovintendent" (a largely honorary position) at the Royal Court.

[1] After 1812, many of his works were done for the Royal Families, including door panels for the bedchamber of Crown Prince (later King) Charles at Rosersberg Palace, a mural of the Four Seasons at Sävstaholm Castle, and Hebe with her father Zeus in the form of an eagle at Rosendal Palace.

In 1824, he created a popular allegorical painting of Crown Princess Josephine returning to Sweden, borne in the clouds by cupids.

[3] In 1828, after Johan Gustaf Sandberg failed to produce an altarpiece commissioned for Saint James's Church, the project was given to Westin, who completed it with a transfiguration of Christ.