Swimming has classically been associated with a distinctive type of extrinsic dental staining. However, its prevalence and characteristics have not been explored in Australia. This case controlled cross-sectional cohort study aimed to determine the prevalence and severity of dental staining among children who swim competitively compared to non-swimmers and its impact on oral health-related quality of life (OHRQL). Parents and children from Western Australian swimming clubs completed a survey assessing swimming routine, risk factors for staining and OHRQL. Intra-oral photographs were taken and staining of anterior teeth was assessed using a modified Lobene Stain Index. A Global Stain Score (GSS) was calculated and compared against age-matched non-swimmer controls. Maxillary anterior teeth from swimmers (n = 400) and non-swimmers (n = 400) were analysed. Staining prevalence was greater in swimmers (83%) than non-swimmers (44%). GSS scores were positively correlated with both the total lifetime swimming hours and practice time (P < 0.05), with a significant difference in GSS between swimmers and non-swimmers (P = <0.001, OR: 6.21). Dietary factors for staining were not significantly correlated with GSS. Swimmers had a greater risk of developing staining than non-swimmers, and this negatively impacted their OHRQL. The extent and intensity of staining were associated with the amount of swimming.