Measurements of streamer velocity reflect the detailed internal microphysics of sprite development that is connected to the effects streamers create in the mesosphere. We report intensified high speed video observations of streamer development acquired at 5,000 to 10,000 frames per second that include the entire altitude range of sprites (∼40–90 km). Downward streamers accelerate to a maximum velocity 3–10% of the speed of light c and then immediately decelerate at an almost constant rate close to 1010 m/s2. This deceleration process dominates the downward streamer propagation in both time and distance. Measurements of the complete dynamics of sprite streamers from initiation to termination can give useful insight into their internal processes.