The aim of this research was to investigate the synergistic effects of peer collaboration and graphic organisers (i.e. mind maps) in Hong Kong science classrooms. Over two hundred Grade Four (i.e. Primary Four) students were assigned to different pedagogical groups, namely, "individualised learning with mind mapping," "collaborative learning without mind mapping" and "collaborative mind mapping," in which they learned a number of science concepts (e.g. living organisms) through such classroom activities as brainstorming tasks and self-reflection exercises. Whilst the quantitative results (i.e. one-way ANOVA) on the elementary science questions revealed that collaborative mind mapping markedly enhanced students' academic achievement, the qualitative findings elicited from their collected mind maps, triangulated by interview data, highlighted the advantages of this integrative learning approach for boosting students' joint construction of conceptual knowledge in science. Valuable insights on the employment of mind maps as peer diagnostic instruments to identify science misconceptions are discussed.