Assisted Reproductive Technology (ART) refers to methods used to provide pregnancy by the manuplation of sperm and ova in vitro. Concern has been raised recently on the safety about the health of children born after ART. Although abnormal genomic imprinting has been shown to be involved in a number of genetic syndromes identified in the pregnancies with ART, there is a lack of evidence linking ART with the Prader-Willi syndrome (PWS) which is caused by the lack of expression of paternally inherited genes on chromosome 15q11–q13. Paternal microdeletion (70%), maternal uniparental disomy (25–30%), and imprinting defect (2–5%) are the main causes of PWS. Here 2-year-old male/female twins, male with upd(15)mat, born to a nonconsanguineous parents following ART is presented. The proband was between 90–97 percentile for height, weight and head circumference on admission. Physical examination showed hypotonia, almond-shaped palpebral fissures, low-set ears, long philtrum, small hands and feet. His history revealed feeding difficulties and delayed developmental milestones. MRI, EEG and EMG were normal. Echocardiography showed supravalvular pulmonary stenosis, which disappeared with aging. Pelvicaliectasis was demonstrated sonographically. Serum biochemical tests, thyroid function tests and amino acid chromatography were normal. Karyotype analysis, FISH analysis for PWS and subtelomeric regions were normal. DNA methylation analysis revealed maternal uniparental disomy. In conclusion this case contributes to the literature in two ways, first the importance of clinical evaluation with molecular testing in the diagnosis of PWS is pointed out, and second ART may have an effect on the occurrence of imprinted diseases such as PWS.