Transdermal drug delivery of diclofenac sodium can reduce gastric side effect, reduce number of doses by gaining sustained release through applying the drug transdermally, avoidance of first pass metabolism, and patient compliance can be improved. Microemulsion is used to modify the drug delivery of the diclofenac sodium in terms of permeability from skin. In this study, Span 20, Tween 80 was selected as surfactant and cosurfactant, isopropyl myristate was selected as lipophilic phase and a mixture of water and dimethyl sulfoxide as a hydrophilic phase. Pseudo ternary diagrams were constructed. The penetration though rat’s skin using franz diffusion cell for different developed diclofenac sodium loaded microemulsions with different hydrophilic phases amount, different amount of diclofenac sodium and using either Span 20 or mixture of Span 20 and Tween 80 were studied. Cumulative amount of diclofenac sodium permeated per unit area in 24 hours was measured. All formulation of drug loaded microemulsion was characterized for their viscosity characteristics and droplet sizes in range of colloidal dispersion system and high flux. The highest flux value for diclofenac sodium through the skin for microemulsion formulation 5 was 223.51ىg/hr.