BACKGROUND AND OBJECTIVES: Juvenile idiopathic arthritis is a childhood rheumatic disease, which can interfere with the trophism and muscular strength of the individual due to persistent pain. Hydrokinesiotherapy may be an alternative in the management of this disease. The objective of this study was to verify the effects of hydrokinesiotherapy on pain, trophism and muscular strength of a child with juvenile rheumatoid arthritis. CASE REPORT: Female patient, 12 years old, diagnosed with juvenile rheumatoid arthritis one year ago. The pain was evaluated by the visual analog scale and the body pain map, the muscular trophism by the perimetry of the arms and thighs, and the muscular strength by isokinetic dynamometry at a speed of 240º. The hydrokinetic therapeutic intervention program (adaptation, warm up, mobility and flexibility, muscle strengthening, cardiorespiratory fitness, balance and proprioception, and relaxation) was carried from October to December 2017, once a week, for 1 hour, totaling 10 sessions. At the end, there was a decrease in pain by 2.7 points (moderate to mild), an increase in muscle trophism of the arms and right thigh in 1cm and an increase in the torque peak (progress ranging from 12.3 to 37.9%) and total work (progress ranging from 18.6 to 76.7%) in all muscle groups analyzed in both knees. CONCLUSION: The hydrokinetic therapeutic intervention plan shown to be an effective strategy to alleviate the pain and increase trophism and muscle strength of the individual with juvenile idiopathic arthritis. Effects of hydrokinesiotherapy in pain, trophism and muscle strength in a child with juvenile idiopathic arthritis. Case report Efeitos da hidrocinesioterapia na dor, no trofismo e na força muscular de uma criança com artrite idiopática juvenil. Relato de caso