The aim of this project was to (a) evaluate the potential of the 2-min walk test to detect declines in gait velocity under dual-task conditions and (b) compare gait velocity overground and on a self-paced treadmill in Parkinson’s disease (PD). In total, 23 individuals with PD completed the 2-min walk test under single- and dual-task (serial 7s) conditions overground and on a self-paced treadmill. There was a significant decrease in gait velocity from single- to dual-task conditions overground (1.32 ± 0.22 to 1.10 ± 0.25 m/s; p < .001) and on the self-paced treadmill (1.24 ± 0.21 to 1.05 ± 0.25 m/s; p < .001). Overground and treadmill velocities were not statistically different from each other; however, differences approached or exceeded the minimal clinical important difference. The 2-min walk test coupled with a cognitive task provides an effective model of identifying dual-task declines in individuals with PD. Further studies comparing overground and self-paced treadmill velocity is warranted in PD.