Objective To enhance the understanding of clinical characteristics and genetic testing of chromosome 4q21/q22 deletion syndrome. Methods Chromosomal microarray analysis was used to detect genetic change in a child with special facial appearance and development delay. Results A 15.26-Mb deletion containing 76 geinges in chromosome 4q21.21q22.2 was identified. Thus, this girl was diagnosed as chromosome 4q21/q22 deletion syndrome. Conclusions Chromosome 4q21/q22 deletion syndrome has varied clinical manifestations including typical characteristics (such as absolute or relative macrocephaly, megalencephaly with a characteristic head shape and facial appearance, profound hypotonia, small hands and feet, short limbs, feeding difficulties), mental retardation/severe developmental delay, and other system abnormalities ( such as congenital heart disease, seizure, kidney cysts, etc). The diagnosis of chromosome 4q21/q22 deletion syndrome relies on chromosomal microarray analysis.