Introduction: Breast cancer survivors, particularly those with stage II-III disease, are exposed to a high burden of cardiotoxic treatments, comorbidities, and psychosocial stressors that may negatively affect cardiovascular health and autonomic regulation. Heart rate variability (HRV) is a non-invasive marker of cardiac autonomic function, yet descriptive data on resting HRV profiles in this population are scarce. Methods: This descriptive cross-sectional study included twelve women with stage II-III breast cancer enrolled in the community-based MAMA_MOVE exercise program. Five women had stage II disease, with a mean age of 58.20 ± 8.14 years, and seven had stage III disease, with a mean age of 58.14 ± 5.79 years. Resting HRV was assessed in a quiet, controlled room using a Polar H10 chest strap. After a 10-minute seated stabilization period, a 5-minute segment of R-R intervals was recorded and exported to Kubios HVR ® software. Outcome measures included heart rate, readiness, parasympathetic (PNS) and sympathetic (SNS) indices, physiological age, time-domain HRV parameters (mean RR, SDNN, RMSSD, Poincaré SD1 and SD2, stress index), and frequency-domain indices (LF and HF power in absolute and relative units, LF/HF ratio), respiratory rate, measurement quality, and self-reported mood. Results: Independent-samples Mann–Whitney U tests revealed no differences between stages II and III for any HRV-related variable (all p > .20). The overall sample showed a heterogeneous resting HRV profile, with wide inter-individual variation across indices. Conclusions: Resting HRV assessment was feasible and well-tolerated in this community-based exercise setting. Although no stage-related differences were identified, the present data provide an initial autonomic profile for women with stage II-III breast cancer and a baseline for future longitudinal exercise studies.