In this work a simple two step method for preparing bimetallic Pd-Pt/MWCNT electrocatalysts via ultrasonic-assisted galvanic-replacement is presented. Firstly, Pd nanoparticles were deposited over MWCNT by micro-emulsion method to synthesize Pd/MWCNT. In a second step the Pd/MWCNT electrocatalyst is immersed in an ultrasonic bath of an aqueous solution containing different Pt concentrations to form a bimetallic Pd-Pt/MWCNT electrocatalyst by galvanic replacement reaction. It is worth to mention that any additive reagent was added during this reaction. The effects of galvanic replacement time, temperature and agitation were investigated. Three different amounts of Pd content were tested: 5, 10 and 20% wt. The catalysts were characterized by TEM, EDS and electrochemical methods. The results showed that bimetallic nanoparticle composition can be tuned up through the galvanic replacement conditions, where the Pt concentration of solution has a very important role. The ultrasound conditions allowed a great performance of the galvanic replacement reaction which leads to achieve the best electrocatalyst in two hour reaction time at room temperature. The electrocatalyst prepared with 10% wt of initial Pd content, 2 hour of reaction time, Pt concentration of 1.25 mM and final composition of Pd:Pt 1:2 showed the highest catalytic activity of all synthesized catalysts. These results showed a simple, efficient an environmental friendly route to synthesized bimetallic electrocatalysts for fuel cell applications.