In the US, 50% of all pediatric outpatient antibiotics prescribed are unnecessary or inappropriate. Less is known about the appropriateness of pediatric outpatient antibiotic prescribing. To identify the overall percentage of outpatient antibiotic prescriptions that are optimal according to guideline recommendations for first-line antibiotic choice and duration. This cross-sectional study obtained data on any clinical encounter for a patient younger than 20 years with at least 1 outpatient oral antibiotic, intramuscular ceftriaxone, or penicillin prescription filled in the state of Tennessee from January 1 to December 31, 2022, from IQVIA's Longitudinal Prescription Claims and Medical Claims databases. Each clinical encounter was assigned a single diagnosis corresponding to the lowest applicable tier in a 3-tier antibiotic tier system. Antibiotics prescribed for tier 1 (nearly always required) or tier 2 (sometimes required) diagnoses were compared with published national guidelines. Antibiotics prescribed for tier 3 (rarely ever required) diagnoses were considered to be suboptimal for both choice and duration. Primary outcome was the percentage of optimal antibiotic prescriptions consistent with guideline recommendations for first-line antibiotic choice and duration. Secondary outcomes were the associations of optimal prescribing by diagnosis, suboptimal antibiotic choice, and patient- and clinician-level factors (ie, age and Social Vulnerability Index) with optimal antibiotic choice, which were measured by odds ratios (ORs) and 95% CIs calculated using a multivariable logistic regression model. A total of 506 633 antibiotics were prescribed in 488 818 clinical encounters (for 247 843 females [50.7%]; mean [SD] age, 8.36 [5.5] years). Of these antibiotics, 21 055 (4.2%) were for tier 1 diagnoses, 288 044 (56.9%) for tier 2 diagnoses, and 197 660 (39.0%) for tier 3 diagnoses. Additionally, 194 906 antibiotics (38.5%) were optimal for antibiotic choice, 259 786 (51.3%) for duration, and 159 050 (31.4%) for both choice and duration. Acute otitis media (AOM) and pharyngitis were the most common indications, with 85 635 of 127 312 (67.3%) clinical encounters for AOM and 42 969 of 76 865 (55.9%) clinical encounters for pharyngitis being optimal for antibiotic choice. Only 257 of 4472 (5.7%) antibiotics prescribed for community-acquired pneumonia had a 5-day duration. Optimal antibiotic choice was more likely in patients who were younger (OR, 0.98; 95% CI, 0.98-0.98) and were less socially vulnerable (OR, 0.84; 95% CI, 0.82-0.86). This cross-sectional study found that less than one-third of antibiotics prescribed to pediatric outpatients in Tennessee were optimal for choice and duration. Four stewardship interventions may be targeted: (1) reduce the number of prescriptions for tier 3 diagnoses, (2) increase optimal prescribing for AOM and pharyngitis, (3) provide clinician education on shorter antibiotic treatment courses for community-acquired pneumonia, and (4) promote optimal antibiotic prescribing in resource-limited settings.