Background Tendon Doppler flow may be associated with tendon pain in symptomatic patients, but the relationship between Doppler flow and pain among athletes who are still competing is unclear. Hypothesis Among active athletes, Doppler flow may partly reflect tendon adaptation to increased mechanical load and/or asymptomatic tendinopathy. Study Design Cross-sectional study; Level of evidence, 3. Methods The Achilles tendons of 61 badminton players (24 elite, 37 recreational) were examined with gray-scale and color Doppler ultrasound. Achilles tendon pain and activity level (badminton training, badminton playing, badminton years) were measured. Results Doppler flow was not associated with current Achilles tendon pain but was associated with an increased anteroposterior tendon diameter (an indicator of tendinopathy) ( P = .02). Athletes who had been playing badminton for longer were more likely to have Doppler flow ( P< .01), and there was a trend toward an association between a greater number of badminton playing hours per week and Doppler flow ( P = .07). Conclusion Achilles tendon Doppler flow appears to be a sign of asymptomatic tendinopathy rather than pain among active athletes. The association between weekly badminton hours and badminton years and Doppler flow suggests that Doppler flow may be a response to mechanical load in this cohort.