A desirable protein bar has a favorable flavor and texture to consumers and a shelf life of at least 6 mo. There are several available protein sources and sweeteners, so it is important to investigate implications on bar sensory properties and shelf stability. A previous study evaluated the impact of protein source and sweetener on bar flavors and sweetness profiles. The objective of this study was to characterize the impact of sweetener and protein source on the texture and shelf life of high protein low carbohydrate bars. The protein bars (15 formulas, replicated twice) consisted of a protein source (whey, milk, or pea) and a sweetener (sucrose, fructose, monk fruit, stevia, or sucralose) with fiber and vegetable shortening. Bars (15 g protein per serving) were placed in moisture barrier pouches and stored 35 d at 35C for accelerated shelf life testing. Instrumental hardness (g) and color measurements (L a b*) were taken and descriptive analysis (DA) of texture was conducted at d 1, 7, 14, 21, 28, and 35. Linear mixed model analyses were conducted for each time point with sugar and protein source and their interaction as fixed effects. Protein source and sweetener had a significant interaction for instrumental and sensory properties (P < 0.05). Bars with whey protein and fructose were harder than other bars until d 21. Whey protein bars, regardless of sweetener, were denser at all time points than pea or milk protein bars. Bars made with pea protein were the driest, least cohesive, and had the fastest rate of breakdown across shelf life (P < 0.05). Whey protein bars had the greatest change in color compared with pea or milk protein, but all protein bar formulas visibly darkened and increased in yellow/red color over time (P < 0.05). Both sweetener and protein source affect protein bar characteristics and should be chosen carefully. These results are important to understand and predict how sugar reduction and/or sweetener replacement affects the sensory and textural properties of protein bars with different protein types.