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Objectives: This cohort study investigated the possible association of dietary nitrate (NO3)/nitrite (NO2) intake and risk of progression to type 2 diabetes (T2D) across different phenotypes of prediabetes (Pre-DM). Methods: A total of 1586 adults diagnosed with Pre-DM [i.e., 60.2% isolated impaired fasting glucose (iIFG), 21% isolated impaired glucose tolerance (iIGT), and 18.8% combined IFG-IGT] in the third (2006–2008) and fourth (2009–2011) examinations of the Tehran Lipid and Glucose Study, were assessed for dietary intake of NO3 and NO2 and were followed up to 2015–2017. Cox proportional hazard models, stratified by Pre-DM phenotypes, were used to plot cumulative hazard curve and calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for developing T2D across tertile categories and per every 100 mg/d NO3 and 2 mg/d NO2 intake exceeded the acceptable daily intake (ADI). Results: The mean age of the participants was 47.2 ± 12.9 years at baseline, and 52.2% were men. Highest intake of NO3 (≥ 645 vs. < 451 mg/d) and NO2 (≥ 11.5 vs. <9.0 mg/d) increased risk of T2D among subjects with iIFG (HR = 1.69, 95% CI = 1.04–2.74 and HR = 2.07, 95% CI = 1.29–3.32). The cumulative hazards were higher in the highest compared to the lowest NO3 and NO2 intake in subjects with iIFG phenotype. Every 100 mg/d of NO3 and 2 mg/d NO2 intake exceeded ADI was associated with an increased risk of progression from iIFG to T2D by 13 and 25%, respectively. Conclusion: High exposure to dietary NO3 and NO2 may be a risk factor for developing T2D in subjects with iIFG. [ABSTRACT FROM AUTHOR]