Transthyretin Amyloid Polyneuropathy (ATTR-PN) is characterized by the deposition of amyloidogenic TTR, particularly in dorsal root ganglia (DRG) and peripheral nerve axons, resulting in sensory axonopathy. Here, we investigated the role of cytoskeleton alterations in peripheral axons from an ATTR-PN mouse model and searched for genetic modifiers in human patient samples. We employed the hTTRA97S knock-in mouse model for ATTR-PN to examine cellular and molecular changes in peripheral axons. Our approach combined proteomic analysis of the sural nerve, live imaging techniques, and pharmacological intervention targeting Rac1. Additionally, DNA samples from individuals diagnosed with early- and late-onset ATTR-PN were analyzed to identify genetic variants in Rac1 and specific regulators potentially associated with the disease-onset. Guided by proteomics of the sural nerve of hTTRA97S mice, which revealed dysregulation of actin-related proteins, we investigated actin organization in mutant neurons. We found a defective actin distribution in growth cones from hTTRA97S DRG neurons, along with a reduction in axonal actin trails, and an associated impairment in the pool of pre-synaptic vesicles. Additionally, microtubule dynamics and axonal transport abnormalities were observed in mutant axons. Importantly, cytoskeletal defects in hTTRA97S neurons preceded axonal degeneration and were mediated by Rac1. Hyperactivation of Rac1 was observed in both hTTRA97S DRG neurites and sciatic nerves of pre-symptomatic mice, and its inhibition rescued cytoskeleton alterations, preventing subsequent degeneration. Remarkably, in ATTR-PN patients with late-onset disease, we identified a variant in the RACGAP1 gene, which encodes for a specific Rac1 inactivator, further supporting the neuroprotective role of Rac1 inhibition. Our findings demonstrate that cytoskeletal defects precede axonal degeneration in ATTR-PN and highlight Rac1 as a promising therapeutic target. The identification of a protective genetic variant in patients corroborates this potential, suggesting a new avenue for therapeutic intervention in ATTR-PN.