Obese adults enjoy perceptually-regulated walking (using perceived exertion; RPE) more than a fixed-intensity. Adding hypoxia (decreased inspired oxygen fraction; FiO2) to perceptually-regulated walking may lead to more favourable exercise-related sensations, due to potential slower velocities for a similar level of physiological stress, which may not occur in the absence of hypoxia at a matched velocity. We investigated if perceptually-regulated interval walking session in hypoxia leads to slower walking velocities vs. normoxia, matches the degree of physiological stress, and preserves exercise-related sensations. Further, we investigated if walking in normoxia at a matched walking velocity selected in hypoxia would produce similar responses in the absence of hypoxia. Ten obese adults (BMI=32±3 kg/m-2) completed a 60-min interval session (15× 2-min: 2-min walking: resting) in hypoxia (FiO2=13%, HYPself-selected) and normoxia (NORself-selected) at a perceptually-regulated velocity (RPE=14, 6-20 Borg scale), and in normoxia at the HYPself-selected velocity (NORimposed). Velocity, heart rate, arterial oxygen saturation (SpO2), and vastus lateralis oxygenation were recorded during walking. Perceived recovery and motivation to exercise were assessed prior to each interval, while breathlessness, limb discomfort and pleasure were evaluated after. Data were averaged for each block of 3 intervals. A 2-way ANOVA analysed the main effect of condition, time and the condition × time interaction. Data are presented as mean±SD. Compared to block 1 (6.20±0.02 km/h-1), velocity was slower during block 4 (6.17±0.06 km/h-1) and 5 (6.16±0.08 km/h-1) and in HYPself-selected vs. NORself-selected (6.17±0.04 vs. 6.23±0.03 km/h-1, respectively, p<0.05). Compared to NORself-selected and NORimposed, heart rate was higher in HYPself-selected (+6±2% and +10±3%, respectively, p<0.05). SpO2 was lower in HYPself-selected vs. NORself-selected and NORimposed (85±1% vs. 97±0% and 98±0%, respectively, p<0.01). Oxyhemoglobin decreased (-3±4%, p<0.01) and deoxyhemoglobin increased (+28±12%, p=0.02) from block 1 to 5, with larger changes in HYPself-selected vs. NORself-selected (oxyhemoglobin: -4±5%, deoxyhemoglobin: +66±10%) and NORimposed (oxyhemoglobin: -18±31%, deoxyhemoglobin: +65±13%, p<0.05). Total hemoglobin decreased from block 1 to 5 (-3±1%, p=0.02). Perceived limb discomfort was lower in HYPself-selected (-21±4%) and NORimposed (-34±6%, p<0.05) vs. NORself-selected. Perceived recovery decreased (-9±2%) and breathlessness increased (+9±1%, p<0.05) from block 1 to 5. Perceived motivation and pleasure were unaffected. Perceptually-regulated interval walking in hypoxia at a lower external workload leads to larger physiological stress and lower exercise-related sensations than normoxia, which does not occur in the absence of hypoxia at a matched walking velocity.