This study explores how public libraries can more effectively support adolescents’ diverse information needs by analyzing their information seeking behavior and library usage experiences. Data were collected through surveys and focus group interviews involving adolescents. The findings indicate that adolescents have a wide range of information needs—including academic work, career planning, leisure, and interpersonal relationships—and tend to rely heavily on video platforms and personal networks to search for information. Although trust in library materials was generally high, adolescents reported significant limitations in accessibility and efficiency during the actual search process. In particular, they experienced difficulties with the library’s classification systems, shelf arrangements, and search keyword formulation. These findings highlight the need for enhanced information services that more precisely address adolescents’ specific needs. Based on these results, this study proposes strategies for designing and delivering public library services that are better aligned with the distinctive characteristics of adolescents’ information needs and information seeking behavior.