The current paper endeavors to present the design, fabrication, and test of a novel valveless piezoelectrically actuated micropump. The proposed micropump mainly comprises a stainless-steel structured chamber with a piezoelectric (PZT) diaphragm as a driving source to propel liquid stream under actuation. During tests, the micropump, operating at the frequency of 250 Hz and the voltage of 160 Vpp, engendered a mean water flowrate up to 0.779 ml/min. In the analysis, the computational fluid dynamics (CFD) software ACE+® was utilized to examine the time-varying flow phenomenon in a full-scale PZT micropump throughout an actuation cycle. The computational approach adopted the transient three-dimensional conservation equations of mass and momentum with the moving boundary specified to represent the movement of the diaphragm. At the frequency ranging from 150 to 250 Hz, the vortex pairs were evidently formed and thereby caused a relatively high pressure drop near the diffuser outlet inside the micropump chamber. Numerical experiments were also carried out by varying the opening angle of the diffuser/nozzle module within the range of 8°－12°, the angle setting of 8° can provide the best performance in term of the maximum pumping flowrate achieved.