The antioxidants, sodium ascorbate and tocopherol, have contrasting effects on the viability of microencapsulated Lactobacillus rhamnosus GG (LGG) spray-dried powders during storage (4 and 25 °C; 32, 57, and 70% relative humidity). The addition of tocopherol improved probiotic viability during storage, while the incorporation of Na-ascorbate alone or in combination with tocopherol had detrimental effects on probiotic survival. The beneficial effect of tocopherol is a consequence of its chemical antioxidative action. The reduced viability in Na-ascorbate containing microcapsule formulations is hypothesized to be due primarily to the production of acetic acids arising from chemical degradation reactions and the catabolism of ascorbate by LGG. This study highlights the importance of considering the detrimental consequences of degradative chemical reactions and the metabolic fate of additives on the viability of probiotics when designing probiotic encapsulant formulations.