Dietary habits are important factors affecting the development of emotion. We have shown that long-term powdered food (PF) feeding in mice increases locomotor activity and social interaction time (SI). Although the increased SI indicates low anxiety, the elevated plus maze test (EPM) shows not only anxiety-related behavior but also impulsive behavior. In this study, we investigated whether the PF feeding causes changes in anxiety-related behavior. Mice fed a PF for 17 weeks were compared with mice fed a standard food. The % of open arm time (OAT) and total number of arm entries were increased in PF-fed mice in the EPM. Moreover, we examined the effects of methylphenidate (MP), dopamine transporter (DAT) and noradrenaline transporter (NAT) inhibitor, atomoxetine (AT), selective NAT inhibitor, GBR12909 (GB), selective DAT inhibitor, and PD168077 (PD), selective D4 receptor agonist, on the changes of EPM in PF-fed mice. MP and AT are clinically used to treat ADHD symptoms. The OAT in PF-fed mice was decreased by MP, AT and PD, but not GB. These results suggest that the PF feeding may cause low anxiety or impulsivity, possibly via NA and DA systems and increase the risk for onset of ADHD-like behaviors.