Water availability is a major factor influencing cotton cultivar performance and sustainable cotton (Gossypium hirsutum L.) production in the southeast USA.  An increased understanding of the response of diverse cotton germplasm lines to supplemental irrigation could aid in future efforts to develop cultivars targeted to irrigated or dryland environments.  In this study, thirteen germplasm lines were selected from the Pee Dee (PD) germplasm collection and evaluated to measure the effect of supplemental irrigation on a number of agronomic and fiber quality traits important to cotton production systems. Most PD germplasm lines receiving supplemental irrigation had increased plant height and lint percent, while boll weight, seed index, fiber length, fiber strength, uniformity index, and micronaire decreased. Cvs. PD-2 and FM-966 did not show a significant response to supplemental irrigation for any of the traits measured. In contrast, PD5377 and PD93009 showed differential responses to supplemental irrigation for five out of the twelve traits measured. This study shows the importance of comparing individual genotype response to supplemental irrigation for agronomic and fiber quality traits to efficiently target genotypes for irrigated or dryland environments.