Presented is a three-dimensional finite element analysis of the seismic behavior of micropiles used in engineering applications, such as construction in earthquake areas, and seismic retrofitting of structure foundation and retaining systems. It is composed of two parts. The first is concerned with analysis of the seismic behavior of a single micropile supporting a superstructure; results obtained with three-dimensional finite element modeling are compared to those obtained from a simplified model based on the Winkler approach. The second part includes a study of the seismic behavior of groups of micropiles. Numerical simulations are conducted to study the variation of the group effect with the variation of micropile spacing, number of micropiles, and the position of the micropile in the group. Analysis of results of numerical simulations shows that the presence of the superstructure induces significant inertial effect, which causes a high increase in the bending moment in the upper part of micropiles; the inertial effect depends mainly on the loading frequency with respect to the fundamental frequency of the soil layer and that of the superstructure. A group effect is observed in groups of micropiles connected by a rigid cap. The group effect depends mainly on micropile spacing, number of micropiles, and position of micropiles in the group. Results show an increase in moment at the head of micropiles with the increase of the micropile spacing (presence of inertial effect) and a concentration of seismic loading on corner micropiles.