Conventional risk factors for prediabetes and type 2 diabetes such as obesity do not completely explain the higher prevalence of prediabetes; therefore, research to investigate the role of other independent risk factors is required. A few cross-sectional studies have reported an association between muscle strength and prediabetes among normal-weight adults, but the longitudinal relationship of muscle strength with incident prediabetes among adults has not been reported. This prospective cohort study was conducted to investigate whether relative handgrip strength in adults predicted prediabetes incidence after 2 years of follow-up. The study was conducted in Ibaraki prefecture, Japan and recruited individuals without prediabetes and diabetes attending lifestyle related medical examinations between April 2016 and March 2017 (n = 2054). Individuals who came for the follow-up medical examinations between April 2018 and March 2019 were included in the analysis (n = 1075). One hundred sixty-nine individuals (15.7%) developed prediabetes after a mean follow-up of 24.2 months (SD = 1.9 months). Multivariable adjusted hazard ratios (aHR) of new prediabetes cases were calculated using Cox regression. Higher baseline relative handgrip strength predicted a lower risk (aHR [95% CI] = 0.38 [0.21-0.71] of prediabetes incidence among adults. Importantly, relative handgrip strength predicted new prediabetes cases among normal weight individuals (aHR [95% CI] = 0.39 [0.16-0.96]). The findings suggest that handgrip strength measurement is useful to identify individuals at high risk of newly diagnosed prediabetes, importantly, among normal weight individuals. The identified individuals may benefit from early intervention to reduce the risk of prediabetes.