<p>The assessing of the variations of mechanical properties is vital for the practical structural applications of refractory high entropy alloys (RHEAs). In this work, the variations in mechanical properties and reliability changes of arc-melted WNbMoTaZr RHEAs were investigated using Weibull statistics by varying the number of remelting operation, sample size, stress gradient and heat treatment conditions. The RHEAs maintained the BCC structure with increased number of remelting operation, but demonstrated enhanced the uniformity of mechanical properties associated with increased Weibull moduli, resulting from the reduction of microstructural defects. For sample size and stress gradient, the properties and reliability of small-sized samples increased due to the reduction of microstructural defects, while the two-parameter Weibull modulus of yield strength for samples with stress gradient decreased from 25.1 to 16.6. After heat treatment at 600 °C, the dendrites were coarsened, and the yield strength as well as its reliability also increased significantly.</p> Graphical abstract <p></p>