Background and Purpose— Deficiencies in stroke preparedness cause major delays to stroke thrombolysis, particularly among economically disadvantaged minorities. We evaluated the effectiveness of a stroke preparedness intervention delivered to preadolescent urban public school children on the stroke knowledge/preparedness of their parents. Methods— We recruited 3070 fourth through sixth graders and 1144 parents from 22 schools into a cluster randomized trial with schools randomized to the HHS (Hip-Hop Stroke) intervention or attentional control (nutrition classes). HHS is a 3-hour culturally tailored, theory-based, multimedia stroke literacy intervention targeting school children, which systematically empowers children to share stroke information with parents. Our main outcome measures were stroke knowledge/preparedness of children and parents using validated surrogates. Results— Among children, it was estimated that 1% (95% confidence interval [CI], 0%–1%) of controls and 2% (95% CI, 1%–4%; P =0.09) of the intervention group demonstrated optimal stroke preparedness (perfect scores on the knowledge/preparedness test) at baseline, increasing to 57% (95% CI, 44%–69%) immediately after the program in the intervention group compared with 1% (95% CI, 0%–1%; P <0.001) among controls. At 3-month follow-up, 24% (95% CI, 15%–33%) of the intervention group retained optimal preparedness, compared with 2% (95% CI, 0%–3%; P <0.001) of controls. Only 3% (95% CI, 2%–4%) of parents in the intervention group could identify all 4 letters of the stroke FAST (Facial droop, Arm weakness, Speech disturbance, Time to call 911) acronym at baseline, increasing to 20% at immediate post-test (95% CI, 16%–24%) and 17% at 3-month delayed post-test (95% CI, 13%–21%; P =0.0062), with no significant changes (3% identification) among controls. Four children, all in the intervention group, called 911 for real-life stroke symptoms, in 1 case overruling a parent’s wait-and-see approach. Conclusions— HHS is an effective, intergenerational model for increasing stroke preparedness among economically disadvantaged minorities. Clinical Trial Registration— URL: https://clinicaltrials.gov . Unique identifier: NCT01497886.