This study investigated the impact of visual timers on 7- to 9-year-old students’ mathematical performance, anticipatory anxiety related to math assessment, and on-task behavior during a timed assessment. Building on previous findings that visual timers reduce anxiety and improve performance, this research further examined how children interact with a Time-Timer and whether its use influenced off-task behaviors. Forty-four children completed a timed mathematical assessment under two counterbalanced conditions: with and without a visible Time-Timer. Results replicated the anxiolytic effect of visual timers indicating significantly lower anticipatory anxiety levels prior to task onset in the Time-Timer condition. However, no significant difference in math performance was observed between conditions. Notably, the Time-Timer condition was associated with a significant reduction in inattentive and motor instability behaviors. This effect was particularly pronounced for children at higher risk for Attention Deficit Hyperactivity Disorder, as measured by the Conners’ questionnaire. Furthermore, engagement with the Time-Timer was highly heterogeneous; while some children never consulted the device, 25% of participants monitored it with high frequency (i.e., more than seven times in a five-minute period). While this study supports the use of visual timers for reducing anxiety and promoting on-task behaviors, it highlights the need to understand individual differences in usage.