OBJECTIVES: 'Quality Cardiopulmonary Resuscitation (QCPR) Classroom' was recently introduced to provide higher-quality Cardiopulmonary Resuscitation (CPR) training. This study aimed to examine whether novel QCPR Classroom training can lead to higher chest-compression quality than standard CPR training. DESIGN: A cluster randomised controlled trial was conducted to compare standard CPR training (control) and QCPR Classroom (intervention). SETTING: Layperson CPR training in Japan. PARTICIPANTS: Six hundred forty-two people aged over 15 years were recruited from among CPR trainees. INTERVENTIONS: CPR performance data were registered without feedback on instrumented Little Anne prototypes for 1 min pretraining and post-training. A large classroom was used in which QCPR Classroom participants could see their CPR performance on a big screen at the front; the control group only received instructor's subjective feedback. PRIMARY AND SECONDARY OUTCOME MEASURES: The primary outcomes were compression depth (mm), rate (compressions per minute (cpm)), percentage of adequate depth (%) and recoil (%). Survey scores were a secondary outcome. The survey included participants' confidence regarding CPR parameters and ease of understanding instructor feedback. RESULTS: In total, 259 and 238 people in the control and QCPR Classroom groups, respectively, were eligible for analysis. After training, the mean compression depth and rate were 56.1±9.8 mm and 119.2±7.3 cpm in the control group and 59.5±7.9 mm and 116.8±5.5 cpm in the QCPR Classroom group. The QCPR Classroom group showed significantly more adequate depth than the control group (p=0.001). There were 39.0% (95% CI 33.8 to 44.2; p<0.0001) and 20.0% improvements (95% CI 15.4 to 24.7; P<0.0001) in the QCPR Classroom and control groups, respectively. The difference in adequate recoil between pretraining and post-training was 2.7% (95% CI -1.7 to 7.1; pre 64.2±36.5% vs post 66.9%±34.6%; p=0.23) and 22.6% in the control and QCPR Classroom groups (95% CI 17.8 to 27.3; pre 64.8±37.5% vs post 87.4%±22.9%; p<0.0001), respectively. CONCLUSIONS: QCPR Classroom helped students achieve high-quality CPR training, especially for proper compression depth and full recoil. For good educational achievement, a novel QCPR Classroom with a metronome sound is recommended.