In cross-sectional studies, patient activation has been associated with better health behaviors, health outcomes, and health-care experiences. Moreover, tailored interventions have led to clinically meaningful improvements in patient activation, as well as health outcomes over time. We tested whether a tailored patient-activation letter communicating bone mineral density (BMD) test results plus an educational brochure improved patient activation scores and levels at 12 and 52 wk post-baseline as the mechanism leading to enhanced bone healthcare. In a randomized, controlled, double-blinded, multicenter pragmatic clinical trial, we randomized 7749 patients ≥50 yr old and presenting for BMD testing at 3 medical centers in the United States between February 2012 and August 2014. The outcome measures were patient activation scores and levels based on 6 items taken from the Patient Activation Measure (PAM) that were administered at the baseline, 12-wk, and 52-wk follow-up interviews. Mean age was 66.6 yr, 83.8% were women, and 75.3% were Non-Hispanic-Whites. Overall, PAM activation scores improved from 58.1 at baseline to 76.4 by 12 wk (p < 0.001) and to 77.2 (p = 0.002) by 52 wk post-baseline. These improvements, however, were not significantly different between the intervention and usual care groups (18.7 vs 18.1, p = 0.176, at 12 wk) in intention-to-treat analyses. PAM activation scores and levels substantially improved at 12 wk and 52 wk, but no differences were observed in these improvements between the intervention and usual care groups. These null findings may have occurred because the tailoring focused on the patient's BMD and fracture risk results, rather than on the patient's BMD and fracture risk results as well as the patient's baseline PAM activation scores or levels.