The co-occurrence of different types of trash in commercial cotton bales compromises the value of cotton, requires more cleaning, and influences the quality of yarn and fabric. To meet the challenge of determining the trash content, two testing methods (i.e., High Volume Instrument [HVI™] and Shirley analyzer [SA]) have been utilized by trade and regulatory offices and laboratories in the cotton industry. However, these methods only report the trash amounts in total, instead of the content for individual trash components. Likely, the complexity of the co-existence of various trash types, including leaves (leaf and bract), seed coats, hulls, and stems, contributes to this limitation. To address this problem, a set of mixtures with known amounts of both clean lint fibers and individual trash components (leaves, seed coats, hulls, stems, and sand/soil) was prepared and the visible/NIR spectral response was related to corresponding trash contents. Comparison of model performances revealed the feasibility of visible/NIR technique in the precise and quantitative determination of total trash, leaf trash, and non-leaf trash components.