The purpose of this study was to investigate whether indices of cardiorespiratory fitness are related to quality of life (QOL) in women survivors of breast cancer. Using the European Organization for Research and Treatment of Cancer QLQ-30 questionnaire, we assessed the QOL of 16 participants (age, 50 ± 9 years; body mass, 66.6 ± 9.6 kg). All participants performed incremental cycle ergometer exercise to determine several indices of cardio-respiratory fitness (e.g., peak oxygen uptake [JOURNAL/jscr/04.02/00124278-200608000-00013/ENTITY_OV0312/v/2017-07-20T235325Z/r/image-pngO2peak, in L·min−1, ml·kg−1·min−1]), peak power output (PPO, in W), PPO/ body mass (W·kg−1), peak heart rate (HRpeak, b·min−1), peak ventilation (VEpeak), and JOURNAL/jscr/04.02/00124278-200608000-00013/ENTITY_OV0312/v/2017-07-20T235325Z/r/image-pngO2 and heart rate (HR) at the ventilatory (VT) and respiratory compensation (RCT) thresholds. Relationships between QOL and variables were assessed using Spearman rank-difference correlation tests. A significant inverse relationship (p < 0.05) was found for QOL scores and values for age (years) and body mass (kg) (ρ = −0.53), %HRpeak@VT (ρ = −0.59) and %VEpeak@VT (ρ = −0.61). A significant positive relationship (p < 0.05) was found for QOL and PPO/body mass (ρ =0.59) and HRpeak (ρ = 0.78), JOURNAL/jscr/04.02/00124278-200608000-00013/ENTITY_OV0312/v/2017-07-20T235325Z/r/image-pngO2@RCT (ml·kg−1·min−1)(ρ = 0.51), power output (PO, expressed as either W or W·kg−1) at RCT, and HR at RCT (ρ = 0.54). No other significant relationship was found between QOL and variables obtained from the tests. In conclusion, these findings highlight possible relationships between cardiorespiratory fitness and well-being in survivors of breast cancer. From a practical point of view, our data emphasize the need for this population to engage in programmed cardiorespiratory exercise training, mainly designed to improve VT and RCT. The improvement of both submaximal indices can have a beneficial effect on QOL.