The portability, sophistication and connectivity prompt users to revolve around multiple applications on the phones at all times. Teenagers are of particular concern because they are usually overoptimistic about their online activity management but underestimate the negative impacts. This study aims to address individual and parental factors related to teenagers' (mainly aged 13 to 18) smartphone addiction tendency (SAT) with a representative sample of parent-child dyads around Taiwan. We try to draw a holistic view of how Taiwan youngsters use their smartphones and how their parents mediate that use by surveying all possible factors related to that use. According to the analytical results, we ascertained that smartphone ownership and dissimilar purposes for surfing the Internet are associated with students' SAT. Online games and trade are related to younger students' SAT, while SNSs is associated with older students' SAT. Additionally, teenagers' cybersecurity knowledge regarding smartphones is negatively related to their SAT. Lastly, we found parent-reported mediation strategies are barely effective, and parents are even unaware of older students’ smartphone use. The implications for suitable interventions in family and school contexts are discussed followed by the analyses.