Background/Objectives: Homocysteine is implicated in endothelial dysfunction, oxidative stress and arterial remodelling. Peripheral artery disease (PAD) is associated with arterial stiffness and may confound this relationship. We examined whether homocysteine was associated with carotid–femoral pulse-wave velocity (cfPWV) in treated hypertensive adults after adjustment for PAD, and whether PAD modified it. Methods: This single-centre cross-sectional study included 366 adults with treated hypertension. Arterial stiffness was measured by cfPWV; high stiffness was cfPWV ≥10 m/s. Homocysteine was analysed per 5 μmol/L increase. Robust linear regression assessed continuous cfPWV, adjusting for age, sex, body-mass index, 24-hour systolic blood pressure, diabetes, chronic kidney disease, smoking, LDL cholesterol and PAD. Subgroup and interaction analyses assessed PAD effect modification. Results: PAD was present in 98 patients and 99 had high arterial stiffness. Median homocysteine was 11.0 μmol/L. Each 5 μmol/L increase in homocysteine was associated with 0.56 m/s higher cfPWV before PAD adjustment and 0.57 m/s higher cfPWV after PAD adjustment. PAD was independently associated with 1.03 m/s higher cfPWV. The homocysteine–cfPWV association remained significant without PAD and was directionally similar but less precise with PAD. There was no significant homocysteine-by-PAD interaction. Patients with elevated homocysteine and PAD had the highest adjusted cfPWV. For high-stiffness discrimination, homocysteine alone had an area under the curve of 0.635, improving to 0.758 with PAD and 0.809 in the fully adjusted model. Conclusions: In hypertensive adults, higher homocysteine was independently associated with greater cfPWV after adjustment for PAD and conventional risk factors. PAD was also independently associated with arterial stiffness but did not attenuate or modify this association. Homocysteine and PAD may provide complementary vascular-risk information.