Gait speed is a measure of health and functioning. Physical and cognitive determinants of gait are amenable to interventions, but best practices remain unclear. We investigated the effects of a 12-month physical and cognitive training (PTCT) on gait speed, dual-task cost in gait speed, and executive functions (EFs) compared with physical training (PT) (ISRCTN52388040). Community-dwelling older adults, who did not meet physical activity recommendations, were recruited (n = 314). PT included supervised walking/balance (once weekly) and resistance/balance training (once weekly), home exercises (2-3 times weekly), and moderate aerobic activity 150 min/week in bouts of >10 min. PTCT included the PT and computer training (CT) on EFs 15-20 min, 3-4 times weekly. The primary outcome was gait speed. Secondary outcomes were 6-min walking distance, dual-task cost in gait speed, and EF (Stroop and Trail Making B-A). The trial was completed by 93% of the participants (age 74.5 [SD3.8] years; 60% women). Mean adherence to supervised sessions was 59%-72% in PT and 62%-77% in PTCT. Home exercises and CT were performed on average 1.9 times/week. Weekly minutes spent in aerobic activities were 188 (median 169) in PT and 207 (median 180) in PTCT. No significant interactions were observed for gait speed (PTCT-PT, 0.02; 95%CI -0.03, 0.08), walking distance (-3.8; -16.9, 9.3) or dual-task cost (-0.22; -1.74, 1.30). Stroop improvement was greater after PTCT than PT (-6.9; -13.0, -0.8). Complementing physical training with EFs training is not essential for promotion of gait speed. For EF's, complementing physical training with targeted cognitive training provides additional benefit.