This paper examines the effects of inoculant type and treatment material quantity on the mechanical and thermal properties of rail vehicle brake discs manufactured from vermicular graphite cast iron/compacted graphite iron (CGI). The in-mold treatment technique was employed in manufacturing the CGI brake discs. The main and interaction effects of inoculant type and treatment material quantity parameters affecting the tensile strength of the CGI brake discs were determined. The results indicate that treatment material quantity has the most significant effect on mechanical properties. Tensile strength was observed to increase as the treatment material quantity increased. The optimum level for manufacturing the CGI brake disc by using the in-mold treatment technique was attained via the combination of SB 5-type inoculant and 625 g treatment material quantity.