Partial trisomy syndrome of chromosome 9 is one of the frequent autosomal trisomies with a well defined phenotype. Here we report two cases with different karyotypes and we aim to compare the phenotypic findings. The first case was an 8.5 months old boy with developmental delay. He had mental and motor retardation, microcephaly, bilateral undescended testes and multiple minor malformations. The karyotype was 46,XY,-7,der(7)t(7;9)(q36;p12) pat. The second case was a 5 year old boy with mental and motor retardation. He had atypical facial appearance with bilateral undescended testes. The karyotype was reported as 47,XY,+del(9)(q22.1 qter)dn[46]/ 46,XY[4]. Partial trisomy 9 syndrome has a wide range of clinical findings depending on the size of the trisomic chromosome segment. Newly diagnosed cases and their chromosome findings will add to the understanding of the syndrome.