Objective: Isovarelic acidemia (IVA) is an autosomal recessive inborn error of the leucine metabolism that is caused by a deficiency of isovaleryl-CoA dehydrogenase (IVD). Recent application of Tandem mass spectrometry to newborn screening has allowed a significant expansion of the recognition of individuals with IVD deficiency. Methods: We characterized clinical findings and IVD mutations in eleven Korean IVA patients with ten unrelated families. Results: Seven patients were identified through newborn screening using MS/MS while the others who did not undergo new born screening were diagnosed after presenting with typical symptoms including a sweaty foot odor. The clinical presentation varied widely, ranging from mental retardation handicap and multiple episodes of metabolic derangement to an asymptomatic stat. All patients treated with L- carnitine and glycine supplementation, together with low protein diet. Direct sequencing analysis identified mutations of IVD gene. Five patient had 4 types of homozygous mutation (c.144+1G＞T, c.457-3_2CA＞GG, c.149G＞T, c.995T＞C) while others were found to be compound heterozygous (c.832A＞G/c.1135T＞G, c.149G＞T/c.457-3_2CA＞GG, c.350G＞A/c.1248A＞T, c.832A＞G/c.851G＞A, c.379G＞A/c.859C＞G). Among 11 patients, three unrelated patients had c.457-3_2CA＞GG and all lived in Jeju island, suggesting a possible founder effect in this population. Conclusions: These results show different spectrums of IVD mutations in Korean patients and reveal that clinical findings are varied.