The paper aims to explore the presence of significant Freudian concepts discernible in the 20th century American Drama with special reference to some of the plays of Eugene O’Neill. Freudian Psychoanalysis has paved the way for an interpretation of the behavior of human beings in the 20th century. The concepts of personal and collective unconscious and Oedipus and Electra complexes have been explored in his plays. The psychological explorations have enriched the interpretation of the characters in his plays.