The invasive Aedes albopictus, commonly known as the Asian tiger mosquito, has spread globally, posing public health risks because of its role as a secondary vector for arboviruses and capacity to transmit pathogens across sylvatic and urban cycles. In Brazil, where Ae. aegypti remains the primary vector of dengue, Zika, and chikungunya viruses; Ae. albopictus is being increasingly monitored because of its ecological plasticity and potential to develop insecticide resistance. Here, we analyzed the genetic diversity of voltage-gated sodium channel (Na) gene in Ae. albopictus populations across Brazil, in which knockdown resistance mutations (kdr) are associated with pyrethroid resistance. We collected Ae. albopictus from 46 Brazilian cities, extracted DNA from individual mosquitoes, and prepared pooled samples for next-generation sequencing. We targeted two Na segments, regions commonly associated with kdr in other mosquito species: IIS6 and IIIS6 segments. High-throughput sequencing and bioinformatics analysis were used to assess haplotype diversity, distribution, and phylogenetic relationships. We identified 20 IIS6 and 24 IIIS6 haplotypes, indicating high genetic diversity within the Na gene among Brazilian Ae. albopictus populations. No kdr mutations were detected despite the documented occurrence of these mutations in Ae. albopictus from other regions of the world. Nonetheless, we observed several synonymous polymorphisms, suggesting ancestral variation and potential for adaptive evolution. Our findings revealed substantial genetic diversity within the Na gene in Brazilian Ae. albopictus populations but no current evidence of pyrethroid resistance-associated kdr mutations. The observed diversity provides a foundation for tracking shifts in allele frequencies that may affect insecticide susceptibility and vector competence. Continuous monitoring of genetic variation is essential to preemptively address the development of resistance in Ae. albopictus and mitigate potential public health risks.