As part of the insulin signalling pathway, Akt influences growth and metabolism. The AKT1 gene G205T (rs1130214) polymorphism has potential functional effects. Thus, we determined whether the G205T polymorphism influences metabolic variables and their responses to aerobic exercise training. Following dietary stabilization, healthy, sedentary, 50- to 75-year-old Caucasian men (n = 51) and women (n = 58) underwent 6 months of aerobic exercise training. Before and after completing the intervention, dual-energy X-ray absorptiometry was used to measure percentage body fat, computed tomography to measure visceral and subcutaneous fat, and oral glucose tolerance testing to measure glucose total area under the curve (AUC), insulin AUC and insulin sensitivity. Taqman assay was used to determine AKT1 G205T genotypes. At baseline, men with the GG genotype (n = 29) had lower maximal oxygen consumption (VO2 max) values (P = 0.026) and higher percentage body fat (P = 0.046), subcutaneous fat (P = 0.021) and insulin AUC (P = 0.003) values than T allele carriers (n = 22). Despite their rather disadvantageous starting values, men with the GG genotype seemed to respond to exercise training more robustly than men with the T allele, highlighted by significantly greater fold change improvements in insulin AUC (P = 0.012) and glucose AUC (P = 0.035). Although the GG group also significantly improved VO2 max with training, the change in VO2 max was not as great as that of the T allele carriers (P = 0.037). In contrast, after accounting for hormone replacement therapy use, none of the variables differed in the women at baseline. As a result of exercise training, women with the T allele (n = 20) had greater fold change improvements in fasting glucose (P = 0.011), glucose AUC (P = 0.017) and insulin sensitivity (P = 0.044) than GG genotype women (n = 38). Our results suggest that the AKT1 G205T polymorphism influences metabolic variables and their responses to aerobic exercise training in older, previously sedentary individuals.