Carpopedal spasm have various causes ranging from dsyselecrolytemia, syndromic, metabolic or endocrine causes. Any of these could cause a decrease in ionized calcium and tetany. Excessive vomiting leading to alkalosis, hypokaleamia and decreased ionised calcium should be kept in mind for early etiological diagnosis of carpopedal spasm. We report a case of 4-year-old boy presenting with a history of recurrent painful spasm and flexion of bilateral hands following excessive vomiting and electrolyte derangement.