Carl Emil Seashore was born on January 28, 1866, in Mörlunda, Hultsfred Municipality, Kalmar County, Sweden to Carl Gustav and Emily Sjostrand. He emigrated with his family to the United States in 1870 and settled in Iowa. The name "Seashore" is a translation of the Swedish surname Sjöstrand. He graduated from Gustavus Adolphus College, St. Peter, Minnesota in 1891, having studied mathematics, music, and classical languages and literature. During his years in college he served as the organist and choir director of a Swedish-Lutheran church and his salary there paid most of his college expenses. Seashore attended Yale when that school had just opened its psychology department under George Trumbull Ladd. In 1895, Seashore was awarded the school's first Ph. D in psychology for his dissertation on the role of inhibition in learning.

After a trip to Europe and a subsequent fellowship at Yale, he accepted a permanent position at the University of Iowa where he spent the remaining 50 years of his life. There, he was eventually made chairman of the department of psychology and Dean of the Graduate School. He was instrumental in the University's decision in 1922 to accept creative work in lieu of theses for graduate degrees in the fine and performing arts, the first public university in the United States to do so.

Seashore was particularly interested in audiology, the psychology of music, the psychology of speech and stuttering, the psychology of the graphic arts and measuring motivation and scholastic aptitude. He devised the Seashore Tests of Musical Ability in 1919, a version of which is still used in schools in the United States. His interests in the fine arts led to a joint effort with Professor Norman Meier and the publication of the Meier-Seashore Art Judgment Test in 1929. His complete publication list from 1893 to 1949 includes 237 books and articles.

Carl E. Seashore died October 16, 1949.