This study investigated the casual jacket design preferences of women aged 50s and 60s and suggested a prototype design for functional clothing. All age groups liked the casual jacket with a length between the waist and hip, a convertible collar, and a single-breasted design. Those in their 50s preferred fitted or semi-fitted casual jackets while those in their 60s preferred semi-fitted casual jackets. Although, there were significant differences between the preferred jacket designs and ready-made brand jacket designs, most brand jacket designs were casual, semi-fitted, middle-hip length, single-breasted, and with stand-rolled or convertible collars. The analysis of the sleeve styles in brand jackets showed that consumers needed designs that are more decorative. Fashion designers for senior citizens need to design elderly clothing that is comfortable, fashionable, functional, and considers a universal design for ease of clothing function. It will also make the senior citizen fashion market more appealing to consumers. To provide jacket designs for senior citizens, we suggested casual jacket designs for embedding a functional device as well as a new jacket design library for women in their 50s and 60s.