The purpose of this study was to investigate solid lipid nanoparticles (SLN) hydrogel for transdermal iontophoretic drug delivery. Triamcinolone acetonide acetate (TAA), a glucocorticoids compound, was employed as the model drug. SLN containing the drug triamcinolone acetonide acetate (TAA-SLN) and their carbopol gel with stable physicochemical properties were prepared. The use of TAA-SLN carbopol gel as a vehicle for the transdermal iontophoretic delivery of TAA was evaluated in vitro using horizontal diffusion cells fitted with porcine ear skin. We found that the TAA-SLN gel possessed good stability, rheological properties, and high electric conductance. Transdermal penetration of TAA from TAA-SLN gel cross the skin tissue was significantly enhanced by iontophoresis. The enhancement of the cumulative penetration amount and the steady-state penetration flux of the penetrated drug were related to the particle size of TAA-SLN and the characteristics of the applied pulse electric current, such as density, frequency, and on/off interval ratio. These results indicated that SLN carbopol gel could be used as a vehicle for transdermal iontophoretic drug delivery under suitable electric conditions.