Microemulsion based gel formulations are successfully used to improve the aqueous solubility and bioavailability of drugs with less aqueous phase solubility. Phase diagram of drug Nandrolone Decanoate (ND) is prepared and studied as three component system. The pseudo-ternary system Ethyl oleate + Kolliphor HS + ethanol (3:1v/v)/water witnessed a small clear zone of 30.25%, which was reduced to 25.30% when ratio reduced to 2:1v/v. And, for another combination of Ethyl oleate + Kolliphor HS + IPA (3:1v/v)/water witnessed clear zone of 28.63%, which was reduced to 19.33% with reduction in ration to 2:1v/v. The purpose of this study is to provide information about the significance of pseudo-ternary phase diagram construction, as an important tool for the development of microemulsion formulation. The performed experimental work results are presented in detail and discussed with regard to prepare a microemulsion based formulation for transdermal drug delivery of the drug.