Introduction: beta-alanine (BA) supplementation may improve cognition and mitigate symptoms of anxiety and depression associated with aging, neurological disorders, and physical exertion, which has been attributed to increases in brain carnosine and/or brain-derived neurotropic factor (BDNF). BA also provides beneficial effects on cognition, mood, and physical performance during military operations; however, whether BA can attenuate mood disruptions and cognitive dysfunction associated with the anticipatory stress prior to simulated military operations is unknown. Purpose: The present study examined the effects of 14 days of BA (12 g center dot day(-1)) supplementation on cognitive function, mood, and circulating BDNF concentrations in recreationally-active, healthy males with limited inflammation and oxidative stress prior to a 24h simulated military operation. Methods: Participants were randomized into BA (n = 10) or placebo (n = 9; PL) for 14 days. Cognitive function, mood, and circulating BDNF were assessed before (PRE) and after (POST) supplementation. Cognition was assessed via multiple object tracking (Neurotracker (TM)), visuomotor reaction time (Dynavision (TM)), mathematical processing (Serial Subtraction Test), and neuropsychological assessments (ANAM (TM)). Mood was assessed using the Profile of Mood States (POMS) questionnaire. After POST testing, subjects underwent a 24h simulated military operation. Results: No change in measures of cognitive function or BDNF concentrations were observed (p > 0.05). However, BA experienced significant reductions (p = 0.046) in subjective feelings of depression, while PL experienced significant reductions (p = 0.021) in feelings of vigor from PRE to POST. Conclusions: High-dose, short-duration BA supplementation does not appear to affect cognitive function or circulating BDNF, but may mitigate the onset of negative mood states in healthy, recreationally-active males prior to a simulated military operation.