Abstract: While mobile phones bring convenience to people's lives, they also cause environmental problems and resource waste. Moreover, limited research exists on the environmental impact of various mobile phone back shells and their recycling. To further promote the green development of the mobile phone industry, this study applied the life cycle assessment method to evaluate the environmental impact, carbon footprint, and cumulative energy demand of two typical mobile phone back shells: one made of a new polycarbonate/polymethyl methacrylate (PC/PMMA) composite material and the other made of traditional glass materials. The assessment covers the entire life cycle stages, including raw material acquisition, transportation, processing, to waste recycling. The results show that all environmental impact indicators of the PC/PMMA mobile phone back shells are lower than those of the glass mobile phone back shells. The carbon emissions of the PC/PMMA mobile phone back shells are 46% lower than those of the glass mobile phone back shells, with the majority (90.3%) occurring during the stages of raw material acquisition and transportation. The carbon emissions of the glass mobile phone back shells mainly concentrate in the transportation and processing stages, accounting for 86.6% of the total emissions. The cumulative energy demand of the PC/PMMA mobile phone back shells is 26.6% lower than that of the glass mobile phone back shells, mainly concentrated in the stage of raw material acquisition, accounting for 76.1% of the total energy consumption. The carbon emissions of the glass mobile phone back shells mainly concentrate in the transportation and production stages, accounting for 84.5% of the total energy consumption. Sensitivity analysis indicates that electricity is the key factor affecting the carbon emissions of the two types of mobile phone back shells. Therefore, promoting the use of PC/PMMA materials in mobile phone back shells is more conducive to the green development of the mobile phone industry. Additionally, controlling the input of bisphenol A and adjusting the energy structure can further reduce carbon emissions.