In this study, the effect of zirconia nanoparticle coating on the chemical and mechanical characteristics of E-glass fibers was investigated for usage in an alkaline environment. E-glass fibers were dip-coated in aqueous zirconia nanoparticle solutions that have varying concentrations of nanoparticles. Tensile tests were conducted on bare and coated fibers to determine the impact of nanoparticles on the strength of fibers. According to the mechanical analysis, the tensile strengths of the fibers were enhanced by 10.2%, 12.2%, 14.6%, and 17.4% for 5%, 10%, 15%, and 20% of nanoparticles in the solutions, respectively. The role of zirconia coating on the alkali resistance of fibers was investigated in a NaOH-based alkaline solution. Zirconia nanoparticle-coated fibers with 15% and 20% solutions were not corroded in the alkaline environment after dwelling for 500 h. The coating also prevented the degradation of mechanical properties, and the aged fibers maintained similar tensile characteristics.