The crystallization kinetics of Zr₅₅Cu₃₀Al₁₀Ni₅ and (Zr₅₅Cu₃₀Al₁₀Ni₅)₉₈Nb₂ melt-spun metallic glasses in non-isothermal and isothermal conditions were studied by differential scanning calorimetry. According to the non-isothermal and isothermal conditions, the crystallization activation energy for the Nb-containing sample is lower than the Nb-free sample, suggesting that crystallization transformation becomes easier by Nb microalloying. The time-temperature-transformation (TTT) diagrams demonstrate that the Nb minor addition delays the onset of crystallization by shifting the incubation time to longer times, but then accelerates the crystallization progress by shortening the endset time of crystallization, yielding a narrower crystallization transformation region. The Avrami exponents for both non-isothermal and isothermal conditions have larger values in Nb-containing sample, revealing increased nucleation …