This study examined in older adults the effects of wearing the Cosmed K4b2 metabolic system with face mask during the 1-mile Rockport Fitness Walking Test (RFWT). A randomised cross-over design was used (13 males, 12 females, age: 67±4 (yrs). Walking time, walking speed and final heart rate were recorded and predicted VO2max calculated. Participants had a constant walking speed during the RFWT (P = 0.24) not influenced by wearing the Cosmed K4b2. Using Bland-Altman analysis, bias for walking time, heart rate and predicted VO2max was not significant. The predicted VO2max wearing the Cosmed K4b2 was within 0.05±0.36 L·min-1. Wearing the Cosmed K4b2 metabolic system with face mask did not influence 1-mile walking performance in older adults. This observation allows the Cosmed K4b2 metabolic system to be used during walking tests in older adults to examine metabolic and physiologic adaptations by controlled exercise interventions.