An effective apparel design process is key to the successful launch of an apparel product. Application of engineering design process theory, the foundation of the design process, may enhance understanding of the apparel design process. Goals of this research were to: (a) interpret actions and decisions made during the apparel design process, (b) determine whether the specific stages of engineering design process theory were used by apparel designers and merchandisers, and (c) determine applicability of engineering design process theory to apparel design. The research method was interpretive qualitative research employing triangulated methods of long interview and observation. Interview questions focused on actions and decisions made during the apparel design process. Inter-rater reliability and respondent validation were used to increase research reliability. Results showed that there is a systematic building block process to designing apparel lines and a direct relationship between engineering design process theory and process steps used by apparel design associates.