Purpose: To examine racial/ethnic differences in participant-reported and device-based estimates of sedentary and physical activity behaviors and correlations between measurement methods in midlife and young-old women. Methods: Data are from 1,257 Study of Women’s Health Across the Nation participants, aged 60–72 who agreed to participate in an accelerometer protocol and had valid wear time (46% White, 26% Black, 12% Chinese, 10% Japanese, 6% Hispanic). Measures from the Kaiser Physical Activity Scale (KPAS) and ActiGraph wGT3X-BT were summarized overall and by race/ethnic groups. Partial Spearman rank order correlation coefficients between the KPAS and accelerometer were computed overall and by race/ethnic groups. Fisher’s z transformation-derived confidence intervals were calculated to evaluate differences in observed correlations in the various race/ethnic groups, compared to White women. Results: Participants spent an average of 7.5 ± 2.1 h·d−1 in sedentary behaviors, 4.5 ± 1.1 h·d−1 and 2.3 ± 0.8 h·d−1 in low or high light intensity physical activity, respectively, and 56 ± 35 min·d−1 in moderate-to-vigorous intensity physical activity. Time spent in each category differed by race/ethnic group. Overall, correlation coefficients comparing the KPAS domain-specific and total physical activity scores with accelerometry were low to moderate (range: 0.062–0.462), and few statistically significant differences in correlations were noted for race/ethnic groups, compared to White women. Conclusions: Study findings complement prior studies describing sedentary and physical activity behaviors using multi-methods in a diverse population of older women, and provide additional evidence on the convergent validity of the KPAS by race/ethnic groups.