Globalization and change in financial structures have had a significant impact on the clothing industry. Sportswear manufacturing is also a subcategory of the clothing industry. The aim of present study was to understand the sport clothing industry environment by using the PEST model to recognize the affecting factors on development of sport clothing industry. This is a qualitative research by using thematic analysis method. Data were also collected in semi-structured interviews based on the literature of the research. The statistical population of this study consisted of founders, managers, board members and sales managers, active manufacturers of clothing industry inside Iran. Purposive sampling method was used for sampling. The results showed that the political factor with developmental, supportive and communication subcategories, economic factor with sub-categories of raw materials, communication and optimization, social factor with subcategories of perceptual, human resources and culture, and the factor of technology with developmental and infrastructure sub-categories on industrial development clothing are impressive. According to research findings, environmental factors from the perspective of activists in this field have a crucial role in the development and growth of Iranian apparel industry and managers, officials, entrepreneurs and investors in this field should pay attention to these factors before making a decision and entering this area.