Objective: We investigated anosmia as a potential biomarker for alterations of personality in Amyotrophic Lateral Sclerosis (ALS). We tested the hypothesis that there would be a significant relationship between olfaction and personality change in patients with ALS. Method: 30 patients with mild to moderate ALS were recruited from University of Iowa Hospitals and Clinics. Participants were administered an odor identification test. A collateral (spouse in most cases) completed the Iowa Scales of Personality Change, which assesses changes in executive functioning/decision-making, social behavior, motivation/hypo-emotionality, emotional reactivity, and distress. Multiple regression analyses were conducted for each domain of personality to test if changes in personality were significantly associated with olfaction while controlling for sex, age, and smoking status. Results: The average odor identification score fell within the 35th percentile, and 80% of the participants had mild to severe anosmia. The results indicated that change in executive functioning/decision-making was significantly associated with smell scores (p < .05, R2 = .788). Within this dimension, there was a significant relationship between olfaction and both planning (95% CI [−7.676, −.629], p < .05) and persistence (95% CI [1.368, 5.820], p < .05). Conclusion(s): Consistent with our prediction, we found that executive functioning/decision-making was significantly associated with olfaction. These findings reflect the proximity between neural systems that subserve olfaction and executive functioning. Further research could determine if these findings are due to decline in the orbitofrontal cortex, which is responsible for executive functioning/decision-making and smell identification. The results suggest that olfaction could provide insight about neural decline in ALS, and perhaps serve as an early biomarker.