Objectives. To test whether a comprehensive safe patient-handling intervention, which successfully reduced overall injury rates among hospital workers in a prior study, was differentially effective for higher-wage workers (nurses) versus low-wage workers (patient care associates [PCAs]). Methods. Data were from a cohort of nurses and PCAs at 2 large hospitals in Boston, Massachusetts. One hospital received the intervention in 2013; the other did not. Using longitudinal survey data from 2012 and 2014 plus longitudinal administrative injury and payroll data, we tested for socioeconomic differences in changes in self-reported safe patient-handling practices, and for socioeconomic differences in changes in injury rates using administrative data. Results. After the intervention, improvements in self-reported patient-handling practices were equivalent for PCAs and for nurses. However, in administrative data, lifting and exertion injuries decreased among nurses (rate ratio [RR] = 0.64; 95% confidence interval [CI] = 0.41, 1.00) but not PCAs (RR = 1.10; 95% CI = 0.74,1.63; P for occupation × intervention interaction = 0.02). Conclusions. Although the population-level injury rate decreased after the intervention, most improvements were among higher-wage workers, widening the socioeconomic gap in injury and exemplifying the inequality paradox. Results have implications for public health intervention development, implementation, and analysis.