While oxidized lipoprotein(a) (oxLp(a)) has been indicated to be involved in atherogenesis more than native lipoprotein(a) (Lp(a)), there is still a need to elucidate the associations among oxLp(a), hypertension, and atherosclerosis. The cardio-ankle vascular index (CAVI) is a recently developed index used to assess arterial stiffness that is independent of blood pressure components. The present study investigated the correlation between oxLp(a) and the CAVI among hypertensive subjects. Clinical data, including general atherosclerotic risk factors, in addition to Lp(a), oxLp(a), and the CAVI, were collected from 72 non-smoking, asymptomatic, and untreated female subjects (mean age: 64.3 years). Correlations between the CAVI and Lp(a) or oxLp(a) were examined in a hypertensive group (n = 34) and a non-hypertensive control group (n = 38). There was a significant and positive correlation between the CAVI and subject age in the control group, while there was a significant and positive correlation between the CAVI and subject age, systolic blood pressure, and oxLp(a) (r = 0.38, p < 0.05) in the hypertensive group. A stepwise multiple linear regression analysis identified the oxLp(a) to be correlated independently, significantly, and positively with the CAVI (β = 0.30, p < 0.05) in the hypertensive group, while this correlation was not significant in the control group. These findings suggest that the oxidative modification of Lp(a) may be associated with arterial stiffness in hypertensive, but not non-hypertensive, female subjects.