The research has the aim of defining the special characteristics of the functionalist fashion design in the 20th century by understanding the essence of functionalism in the sociocultural contexts and studying functionalism in fashion design and architectural and product design by the comparative. Giving careful consideration to functionalist fashion design in the 20th century makes it possible to foresee the way of fashion design to meet the needs of the moderns and men of the future world. To obtain the purposes, documentary study and comparative study have been executed. Main results are as follows. Functionalism stressed in the beginning of the 20th century can be defined and categorized using three analogies, mechanical analogy of futuristic quality based on mechanical aesthetics and standardization by mass production, organic analogy in which the perfect beauty of nature is stressed on, moral analogy of fitness for purpose and absence of ornament based on integrity and sincerity. In while, functionalism in 1990s has been developed in different ways from those analogies. In comparative studies, functionalist fashion design and architectural and product design have the dissimilarity as well as the similarity of formative features. Since fashion design has much closer relation to human body and movements. it has been expressed considering a division of men and women and the places and times for the designs more than other designs.