Background: Chemotherapy-induced peripheral neuropathy (CIPN) is a dose-limiting toxicity of several commonly used chemotherapy drugs including taxanes, vinca alkaloids, and platinum compounds. Development of CIPN is highly variable, both in self-reported symptoms and functional consequences, and can be severe enough to alter dose intensity. The purpose of this pilot study was to gain insight into the natural history of both patient-reported and objective functional symptoms in breast cancer patients undergoing taxane-based chemotherapy. Methods: Thirty-two breast cancer patients (31 female/ 1 male; 47.6 ± 11.2 yr; n = 16 stage II/ n = 16 stage III) were enrolled. Patients completed self-reports of symptoms and function (e.g., EORTC QLQ-CIPN20) and objective measures of physical function (i.e., balance and gait testing) in an outpatient oncology clinic at five timepoints: (1) prior to starting chemotherapy to provide a baseline, (2-4) before starting subsequent chemotherapy cycles, and (5) 1-3 months after receiving their last taxane infusion. The balance task consisted of quietly standing on a balance plate with eyes closed. Gait testing consisted of 10 meter overground walking. All data were recorded by trained clinical personnel. Results: Significant negative changes in both patient-reported outcomes and objective functional measures were observed. Decreased balance (i.e., increased center of pressure dispersion quantified by 95% confidence ellipse areas) was observed as early as after the first chemotherapy cycle [45% increase, p = 0.01] and progressed with cumulative exposure [87% increase, p = 0.002]. Patients also demonstrated slower walking speeds as they progressed through treatment [4% decrease in speed, p = 0.01]. These functional deficits were mirrored with increased patient-reported symptom severity for all EORTC QLQ-CIPN20 subscales [all p < 0.05]. Conclusions: This is the first study to longitudinally assess patient-reported symptoms concurrently with balance and gait testing in patients undergoing taxane therapy. Taxane treatment was associated with the development of clinically relevant problems in both CIPN symptoms and patient function.