The study investigated the effects of germinated papaya seed and a mixture of germinated papaya seed and chitosan on growth and haematological parameters in broilers stocked in high-density pens from 15 to 28 days old. A total of 490 broiler chicks were distributed into four groups, including CONT (chicks receiving basal feed and raised under normal density [10 chicks per m 2 ]), HSD (chicks receiving basal feed and raised under high density [20 chicks per m 2 ]), HSD-P (chicks receiving 0.5% germinated papaya seed flour and raised under high density) and HSD-PC (chicks receiving 0.5% germinated papaya seed flour and 0.2% chitosan, and raised in high-density condition). Growth and feed intake were measured weekly, while blood was collected on day 28. Despite being lower (P < 0.05) than CONT, HSD-P and HSD-PC chickens consumed more (P < 0.05) feed than HSD chickens. Body weight and weight gain were lower (P < 0.05) in HSD compared to the CONT, HSD-P and HSD-PC groups. The European Production Higher Efficiency Factor (EPEF) tended (P = 0.06) to be higher in HSD-PC than in HSD chicks. While there was no significant effect of the treatments on complete blood counts and serum biochemical parameters, serum creatinine concentration was higher (P < 0.05) in HSD and HSD-P than in CONT and HSD-PC. In conclusion, germinated papaya seeds or a mixture of germinated papaya seeds and chitosan improved broiler production performance and kidney health while alleviating muscle protein catabolism in high-density pens from days 15 to 28.