Protein bar consumption by Americans has increased in recent years as has an interest for natural non-nutritive sweeteners. Each sweetener has unique temporal properties that can influence sensory properties. The objective of this study was to characterize the temporal sensory properties of low carbohydrate whey protein bars with different sweeteners using 3 temporal methods: Time Intensity (TI), Temporal Dominance of Sensations (TDS), and Temporal Check-All-That-Apply (TCATA). A category survey of commercial protein bars (n = 12) was conducted to identify a target sweet taste intensity. Subsequently, protein bars were formulated with whey protein isolate (WPI), fiber syrup, shortening, and each sweetener. Iso-sweet concentrations for each sweetener (sucralose, sucrose, fructose, stevia, monk fruit) in WPI bars were established using magnitude estimation scaling (n = 8 panelists, 3 replications) followed by confirmation by alternative forced choice tests (n = 40). Sweetener blends were subsequently created with reduced bitter and metallic tastes. Temporal sensory profiling (TI, TDS and TCATA) was conducted on protein bars with each sweetener and sweetener blend by a trained panel (n = 8). Consumer acceptance testing was conducted on selected sweeteners in bars. Data were analyzed by appropriate univariate analyses. Protein bars sweetened with fructose or sucrose were characterized by initial intense sweetness that quickly faded. Sucralose displayed a sweet taste profile that was most similar to fructose or sucrose, but differed by metallic taste and lingering sweetness after expectoration. Monk fruit and stevia were slower in sweet taste onset (P < 0.05) and were characterized by bitter and metallic aftertastes and lingering sweetness. These sweeteners were characterized by initial dominant sweet taste, then by bitter and metallic tastes by TDS and TCATA. Sucralose and a blend of monk fruit with fructose were the most similar to sucrose sweetened bars (P > 0.05), and these bars were preferred by consumers (P < 0.05). Knowledge of the temporal properties of non-nutritive sweeteners and the effects of the food matrix on sweeteners are important to understand how sugar reduction and/or sweetener replacement will affect the sensory properties of protein bars.