Seyfert was born in Cleveland, Ohio, and studied at Harvard where he graduated in 1933 and obtained his PhD in 1936. He worked at the McDonald Observatory in Texas from 1936 to 1940, the Mount Wilson Observatory in California from 1940 to 1942 and the Case Institute of Technology in Cleveland, Ohio from 1942 to 1946. Seyfert then moved to the Vanderbilt University in Tennessee as associate professor and where from 1951 until his death he was director of the Dyer Observatory.

In 1943, while observing at Mount Wilson, Seyfert discovered an unusual class of spiral galaxies that have since been named for him. Optically they presented a very small intensely bright nucleus; spectroscopically they had very broad emission lines indicating the presence of very hot gas moving at considerable velocities.

Since their discovery Seyfert galaxies have become even more puzzling as they are now recognized to be emitters of prodigious amounts of energy from a very compact area. Energy is released not just in the form of light but also as x-rays and radio and infrared waves. It is felt that they are related in some way to quasars, discovered in the 1960s, although possessing a less powerful source of energy.