Aim: This study was aimed to assess seasonal/geographical distribution and sequence diversity of partial hexon gene for human adenoviruses (HAdVs) within raw sewages (RS) and activated sludges (AS). Methods and Results: Assessments were based on high-throughput sequencing (HTS) for polymerase chain reaction (PCR)-amplified 128-bp partial hexon gene fragments and followed by principal coordinate analyses (PCoA) for revealed sequences. Sequencing results showed that the majority of sequences (>90%) for the RS or AS samples were identical to HAdV type 41 of species F, while rest of few sequences belonged to HAdV species-D and -C were only occurred rarely without significant seasonal/geographical variation. The partial hexon genes were highly diverse as many sequence types and operational taxonomic unit groups were noticed among the matched sequences. Conclusions: This study demonstrated that HAdV-41 was constantly appeared in the RS and AS samples from Taiwan throughout the year without significant seasonal or geographical variations; but, had high sequence diverse noticed for the 128-bp partial hexon gene fragments. Significance and Impact of the Study: High-throughput-sequencing results provided better insights of HAdV distribution and genetic diversity for raw sewage and AS samples allowing some probable biases for cloning-sequencing approach to be defeated and further providing public health awareness regarding viral-contaminated sewages or sludges.