This study focused on evaluating the phytoextraction of heavy metals (Co, Pb, and Zn) induced by bioaugmentation of button mushroom compost (BMC) in Helianthus annuus (sunflower). When the potential ability of BMC to solubilize heavy metals was assessed in a batch experiment, the inoculation with BMC could increase more the concentrations of water-soluble Co, Pb, and Cd by 35, 25, and 45% respectively, compared to those of non-inoculated soils. BMC-assisted growth promotion and metal uptake in H. annuus was also evaluated in a pot experiment. In comparison with non-inoculated seedlings, the inoculation led to an increase in the growth of H. annuus by 27, 25, and 28% in Co-, Pb-, and Zn-contaminated soils, respectively. Moreover, enhanced accumulation of Co, Pb, and Zn in the shoot and root systems was observed in inoculated plants, where metal the translocation from root to the above-ground tissues was also found to be enhanced by the BMC. Evidently, these results suggest that the BMC could be effectively employed in enhancing the phytoextraction of Co, Pb, and Zn from contaminated soils.