The Mental Toughness Questionnaire-48 (MTQ48; Clough, Earle, & Sewell, 2002) is the most utilised instrument to measure Mental Toughness in sport (Gucciardi, Hanton, & Mallett, 2012). To date, preliminary research (Gucciardi et al., 2012; Perry et al., 2013) examining the factorial validity of the MTQ48 in athlete samples has yielded equivocal findings. The aim of this paper was to re-examine the factorial validity of the four- and six-factor models of the MTQ48 in moderate (n = 480) and large (n = 1206) independent student athlete samples. Using confirmatory factor analyses, findings revealed little support for the hypothesised models of the MTQ48 in both samples. The results support those found by Gucciardi et al. and Perry et al. and suggest that, in its current form, the MTQ48 may not be a valid measure of the 4/6Cs model of mental toughness when using student athletes.