OBJECTIVE: The limitations of Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT)’s embedded validity measures (EVMs) are well-documented, as estimates suggest up to 35% of invalid baseline performances go undetected. Few studies have examined standalone performance validity tests (PVT) as a supplement to ImPACT’s EVMs. METHOD: College athletes (n = 1,213) were administered a preseason baseline assessment that included ImPACT and the Rey Dot Counting Test (DCT), a standalone PVT, among other measures. RESULTS: Sixty-nine athletes (5.69%) met criteria for suboptimal effort on either ImPACT or the DCT. The DCT detected more cases of suboptimal effort (n = 50) than ImPACT (n = 21). A chi2 test of independence detected significant disagreement between the two measures, as only two individuals produced suboptimal effort on both (chi2(2) = 1.568, p = .210). Despite this disagreement, there were significant differences between the suboptimal effort DCT group and the adequate effort DCT group across all four ImPACT neurocognitive domains (U = 19,225.000, p < .001; U = 17,859.000, p < .001; U = 13,854.000, p < .001; U = 17,850.500, p < .001). CONCLUSIONS: The DCT appears to detect suboptimal effort otherwise undetected by ImPACT's EVMs.