The present study investigated the LDL-cholesterol (LDL-C)-lowering effects of psyllium in Brazilian dyslipidaemic children and adolescents. A total of fifty-one individuals (6–19 years) with mild-to-moderate hypercholesterolaemia were evaluated by conducting a randomised, double-blind, placebo-controlled, parallel clinical trial. Over an 8-week trial period, the participants were randomly allocated to one of two groups (control: n 25 and psyllium: n 26) using a computer-generated random number sequence. Fasting blood samples, dietary records and anthropometric data were collected. Both groups were treated with the National Cholesterol Education Program Step 2 diet for 6 weeks before randomisation. After this run-in period, a daily supplement of 7·0 g psyllium was given to the intervention group, while an equivalent amount of cellulose was given to the control group. Statistically significant changes between the control and intervention groups over time were observed for total cholesterol (7·7 %; − 0·39 mmol/l; P= 0·003) and LDL-C (10·7 %; − 0·36 mmol/l; P= 0·01). None of the participants reported any aversion to the smell, taste, appearance or texture of psyllium. No serious adverse effects were reported during the study. In addition to causing a significant reduction in LDL-C concentrations, psyllium therapy was found to be both safe and acceptable for the treatment of hypercholesterolaemic children and adolescents.