Up to half of patients with ALS develop cognitive impairment during the course of the illness. Despite this, there is no simple tool for screening patients in the clinical setting. This study examines the sensitivity, specificity and accuracy of the ALS Cognitive Behavioral Screen (ALS-CBS). We administered the measure to 112 ALS patients, including 31 who also underwent comprehensive neuropsychological testing. Screen results were validated by determining the accuracy against the full battery. Optimal cut-off scores for predicting the correct diagnosis were determined, and mean scores were compared between patients, controls and different diagnostic groups. The results demonstrated that mean cognitive scores differed between ALS and normal controls (p < 0.0001). The cognitive section differentiated ALS-FTD from other ALS patients with 100% accuracy. Cognitively normal ALS patients could be distinguished from those with any cognitive deficit with 71% specificity and 85% sensitivity. A separate behavioral score was significantly lower in the ALS cohort compared to controls (p < 0.0001) and predicted ALS-FTD with 80% sensitivity and 88% specificity. In conclusion, the ALS-CBS can aid in detecting cognitive and behavioral impairment in a clinical setting, although it does not replace formal diagnostic assessment. Further validation with larger sample sizes will clarify its clinical utility.