INTRODUCTION: Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative disease with no known cure, limited treatment options with minimal benefits, and significant unmet need for disease modifying therapies. AIMS: This study investigated memantines impact on ALS progression, with an additional focus on the effects of memantine on cognitive and behavioral changes associated with the disease. METHODS: A randomized, double-blind, placebo-controlled clinical trial was conducted from December 2018 to September 2020. ALS patients were enrolled in-person and remotely across 13 sites in the United States. Participants were randomized to memantine (20 mg twice daily) or placebo in a 2:1 ratio and completed 36 weeks of treatment. The primary outcome of disease progression was assessed by the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R), and blood was collected for biomarker analysis. RESULTS: Of the 99 participants enrolled in the study, 89 were randomized to memantine or placebo (ages 24-83 years, male-to-female ratio ~3:2). Fifty-two participants completed the study treatment with no significant differences in disease progression, biomarker changes (including neurofilament light chain [NfL]), or neuropsychiatric testing noted between the groups. Initial NfL values correlated with the rate of ALSFRS-R decline. DISCUSSION: In this study, memantine did not impact ALS disease progression or neuropsychiatric symptoms. Trials with remote enrollment may help trial participation and success.