In September 1915, he entered Tarkio College in Missouri. Although he initially majored in English, he switched to chemistry under the influence of Arthur Pardee, head of that department. Carothers so excelled in chemistry that before graduation he was made a chemistry instructor and studied for as well as taught the senior course when Pardee left to become chairman of the chemistry department at the University of South Dakota. He graduated from Tarkio in 1920 at the age of 24 with a bachelor of science degree. Then he went to the University of Illinois for his master of arts degree, which he received in 1921 under the guidance of Professor Carl Marvel.