The gut-brain axis plays a key role in the bidirectional communication between the gastrointestinal system and the brain, with gut microbiota significantly influencing cognitive function. While synbiotic and probiotic interventions have shown potential cognitive benefits, results across studies remain mixed. This randomized, controlled, repeated-measures study investigated the effects of a 15-day synbiotic intervention on cognitive performance in 28 healthy women (aged 18 32), assigned to either a synbiotic or no-treatment control group. Cognitive performance was assessed before and after the intervention using the Parametric Auditory Working Memory Task and the Integrated Visual and Auditory Continuous Performance Test (IVA CPT). Compared to the control group, participants in the synbiotic group demonstrated selective improvements in attention, particularly in overall visual attention and visual sustained attention, as indicated by significant group-by-time interactions (ps < .05). No significant changes were observed in auditory working memory or inhibitory control. These results suggest that short-term synbiotic supplementation may selectively enhance visual attention without broadly affecting executive functions.