Strain-rate dependence of preferential occurrence of dynamic recrystallization (DRX) at triple junction (TJ) in copper polycrystal was investigated in tension at 873K and under strain rates from 4.2 x 10(-5) to 4.2 x 10(-3) s(-1). DRX nucleation began to appear preferentially at TJs at around 0.01 strain. This strain was only about 1/10 to 1/20 of the peak strain. Probability of the DRX nucleation at TJ increased monotonically with increasing strain. Furthermore, the probability strongly depended also on the strain rate; with decreasing strain rate, DRX nucleation at TJ started at lower strain and the probability became higher at a fixed strain. More than 80% of the nucleated grains at TJs were twins. The observed probability of the DRX nucleation at TJ showed close relationship with amount of grain-boundary sliding, fold formation, misorientation angle composing TJ, and angle between tensile axis and sliding grain boundary. Mechanisms of the strain-rate dependence of preferential DRX nucleation and twin formation at TJ are discussed in detail in relation with the above factors.