ASTM E1820-11, the most widely adopted standard for the determination of fracture toughness parameters, recommends two ductile crack growth correction methods for the evaluation of the J-integral parameter, viz., the basic test (BT) method and the resistance curve test (RC) method. In the present work, a comparison between the fracture toughness parameters obtained using these two methods for heat-treated Zr-2.5Nb alloy at 25°C and 300°C is presented. In order to examine the influence of a material's microstructural condition on the fracture toughness results obtained via these two methods, Zr-2.5Nb alloy was investigated under six solution heat-treated conditions after getting soaked at 850°C, 870°C, or 890°C for either 15 min or 30 min followed by water quenching. The BT method predicted a higher J parameter than the RC method for a given crack length. This deviation in the magnitude of J increased with increasing crack length and was found to be almost twice as much at room temperature as the deviation observed at 300°C. For smaller crack lengths (i.e., up to a/W < 0.54), the J parameters determined using the two methods showed insignificant deviation (<5 %). However, such deviation reached ∼20 %, corresponding to ∼0.63 a/W. Values of fracture toughness parameters such as JQ, Jmax, and dJ/da evaluated using the BT method were found to be higher than those obtained using the RC method. However, deviations in the JQ and Jmax parameters determined by the two methods were insignificant (less than ∼6 %), whereas the deviation in the dJ/da parameter was ∼15 %. The RC method, in contrast to the BT method, provides a marginally conservative estimation of the fracture toughness. The parameter α used in the BT method was observed to control the extent of deviation in the J–R curves derived using these methods.