This study aimed to explore the incidence and clinical characteristics of multiple complications in children with Kawasaki disease (KD). All patients were diagnosed in our hospital between January 2016 and December 2020. A total of 640 cases were included, 43 patients had coronary artery aneurysm, 51 patients had coronary artery dilation, and 546 patients had no coronary artery damage. The patients were divided into three subgroups based on age: < 1 year old, 1-5 years old, and > 5 years old. The multiple complications of all the KD children and the correlation between extracardiac complications and cardiovascular complications were analyzed. Among the 640 KD children, most were 1-5 years old (415/640, 64.8%). Children < 1 year old (31.6%) and > 5 years old (28.3%) were more likely to have cardiovascular complications. The incidence of respiratory complications was highest in 1-5 year olds (57.1%). Involvement of the digestive and the hematological systems gradually decreased with age, whereas involvement of the nervous system, the urinary system, and the joints gradually increased with age. The incidence of cardiovascular injury with extracardiac complications (22.3%) was higher than that without extracardiac complications (16.3%), although the difference was not statistically significant (p > 0.05). Conclusions: KD can be complicated by multiple-organ injury but there was no significant relationship between the occurrence of extracardiac complications and cardiovascular complications.