In the present study, the transient performance of the viscous micropump will be investigated numerically. The viscous micropump's operation depends mainly on viscous forces and can operate in any situation where viscous forces are dominant. All the micropump calculations are reported in nondimensional quantities, which allows for the prediction of the micropump performance, regardless of the dimensions or the fluid that is used. The effect of the microchannel height, rotor eccentricity, Reynolds number, and pump load on the transient performance of the viscous micropump has been studied in detail. The steady state performance was compared with the available experimental data and was found to be in a very good agreement. The rotor eccentricity was determined to be the parameter that affected the transient performance of the micropump the most significantly. This work provides a foundation for future research on the subject of fluid phenomena in viscous micropumps.