PURPOSE: Baloxavir marboxil is a novel antiviral agent for influenza, introduced into clinical practice in 2018. A concern remains about the variant virus with reduced susceptibility after baloxavir exposure and its clinical consequences such as healthcare-seeking behavior. METHODS: Using a healthcare database in Japan, we compared the medical resource use following baloxavir and neuraminidase inhibitors (NAIs) treatment among children aged 7-15 years. The study period was from December 2018 to March 2019. The primary endpoint was the composite of hospitalization, laboratory and radiological tests, and antibiotic use over 1-9 days of antiviral treatment. As exploratory analyses, secondary outcomes being each single component of the primary composite were assessed and subgroup analyses comparing baloxavir with each NAI were done. RESULTS: Data from 115 867 prescriptions in 115 238 children were analyzed (median age: 10 years; severe influenza risk in 26%; baloxavir accounting for 43%). Overall, baloxavir use did not increase subsequent medical resource utilization in the composite endpoint (adjusted odds ratio [aOR]: 1.04; 95% confidence interval [CI]: 0.99-1.09; P = 0.14), as were likelihoods of other secondary outcomes. In the subgroup analysis, baloxavir use was associated with higher medical resource use than oseltamivir (aOR: 1.21; 95% CI: 1.13-1.31; P < 0.001) and lower resource use than zanamivir (aOR: 0.93; 95% CI 0.86-1.00; P = 0.040). CONCLUSIONS: Based on a single-year experience in Japan, prescribing baloxavir rather than NAIs did not increase medical resource utilization within 9 days of treatment, except in one exploratory comparison with oseltamivir.