Young people’s political engagements are important to the development of democracy. Though described as reluctant to engage in politics, when young people are invited to participate in politics on their own terms, they are more willing to participate. Second screening - using a supplement device alongside TV watching - is assumed to be a potentially effective tool to engage young people. Enabled by communication technology such as portable digital devices, wireless Internet accessibility, and extensive operating systems which make the portable devices “smart” (facilitating wider software, Internet, and multi-media functionality), second screening creates a hybrid media environment. This study aims to explore whether and what media technological attributes potentially work on young people's sense of political efficacy during second screening activities. Incorporating Eveland’s "mix-of-attributes" framework, a mixed-method design was developed to examine media effects through media technological attributes. Two focus group interviews were conducted to develop a set of perceived technological attributes of the convergent media use during second screening. Seven attributes were developed: easy access, recency, user control, hypertextuality, meantime manner, convenience, and lack of hierarchy. These attributes are expected to have potential influences on people’s political efficacy. The direct and indirect relationships among perceived technological attributes, second screening, and Internet political efficacy were tested through a survey. The measurement items of perceived technological attributes were examined. This paper 1) develops technological attributes potentially influencing youth political efficacy, 2) generates measurement items to represent the construct, 3) assesses the validity of the items, and 4) tests the direct relationships between technological attributes and Internet political efficacy, as well as their indirect relationships through second screening.Understanding media effects through its technological attributes not only advances media effect theory by addressing the challenge of understanding continuous media convergence and hybridization, but also provides practical implications for media users and creators. Besides, communicators can develop better media strategies to engage and mobilize the public once we understand what specific technological attributes are at play. However, this study by no means downplays the importance of social and human factors. This paper takes a middle route between technology determinism and social constructivism.