Stringent emission levels challenge automotive industries to come up with innovative ways of improving existing technologies. In advancing diesel engine technology, the key factor lies in further developing a piezoelectric fuel injector in the common-rail system. A direct acting piezoelectric fuel injector prototype for the common-rail system was developed to preserve the lifetime of the actuator, achieve an adequate needle lift, and response quickly. Through analytical work and ANSYS simulations, problems were encountered on the initial designs. These problems were overcome with successive design improvements. Simulations and analytical estimations provide evidence on the potential performance on these improvements. After design iterations, a prototype was fabricated according to the final design. Experimental work further validated that the fuel injector designed is capable of meeting the requirements. Problems with the test results are discussed for further improvements on the design.