Helium-induced defect nucleation and accumulation in polycrystalline W and W-0.5wt.%ZrC  (W-ZrC) were studied in-situ using the transmission electron microscopy (TEM) combined with 40 keV He⁺ irradiation at 800 and 1000 °С at the maximum damage level of 1 dpa.  Radiation-induced dislocation loops were not observed in the current study. W-ZrC was found to be less susceptible to irradiation damage in terms of helium bubble formation and growth, especially at lower temperature (800 ^oC) when vacancies were less mobile. The ZrC particles present in the W matrix pin the forming helium bubbles via interaction between C atom and neighbouring W atom at vacancies. This reduces the capability of helium to trap a vacancy which is required to form the bubble core and, as a consequence, delays, the bubble nucleation. At 1000 ^oC, significant bubble growth occurred in both materials and all the present bubbles transitioned from spherical to faceted shape, whereas at 800 ^oC, faceted helium bubble population was dominated in W.