His style is defined by a directness that avoids sentimental poses. Otis often worked as a copyist. He translated oil paintings by John Singleton Copley into prints for a wider audience. His portraits of Samuel Adams and Edward Everett show a focus on character. He used light to define the physical presence of his subjects. He did not use unnecessary ornamentation. His work includes depictions of Native American leaders such as Kanapima.

Collectors value Otis for his role in the history of American printmaking. His works provide a visual record of the early nineteenth century. He was a practical and observant artist. The simplicity of his compositions, such as his studies of boat-houses, fits in modern interiors. These prints offer a connection to the origins of American printmaking. His portraits remain a primary source for the study of early American political figures.