Human milk oligosaccharides (HMOs) are crucial bioactive components in human milk, known for supporting immunity, gut and neurodevelopment(1,2). However, their effects on cognition remain underexplored. Therefore, this study investigated the cognitive effects of dietary supplementation with HMOs—neutral (nHMO), sialylated (sHMO), and combined HMOs (cHMO)—on working memory performance in developing piglets. Three days old, sixty-four male piglets (Sus scrofa – Large White × Duroc × Belgian Landrace) were randomised into four groups and fed a standard pig milk replacer with the following supplements: control (methyl cellulose at 1.8 g/L), neutral HMO (2′-FL at 1.8 g/L), sialylated HMOs (3′-SL:6′-SL in a 1:2.5 ratio at 1.8 g/L), combined HMOs (70% 2′-FL and 30% 3′-SL:6′-SL in a 1:2.5 ratio at 1.8 g/L). Working memory was assessed on postnatal days 35 and 36 using a novel five-board apparatus developed by our research team. Each piglet completed 16 trials over two days, with four trials conducted in the morning and four in the afternoon each day. A working-memory mistake was recorded whenever a piglet revisited an inaccessible milk bowl. Total mistakes were analysed using a general linear model with univariate analysis of variance. The experimental protocol was approved by the Charles Sturt University Animal Care and Ethics Committee (A23566). Results demonstrated that the mean total number of mistakes was 11.70, 12.59, and 14.62 in the sHMO, cHMO, and nHMO groups, respectively, representing 43.3%, 39.0%, and 29.2% fewer mistakes, respectively, compared with the control group. Therefore, these findings suggest that early-life HMO supplementation, particularly with sialylated and combined formulations, improves working-memory performance in developing piglets. The benefits observed under cognitively demanding conditions suggest that HMOs may support cognitive flexibility and the neural processes involved in the retention and updating of spatial information. This study provides further evidence that early-life nutrition can influence cognitive development and behavioural adaptability.