Root-knot nematodes (RKN) infect a large number of plant species triggering the formation of galls by inducing vascular cells to reenter the cell cycle. These nematodes infect the host root and usurp the plant cell cycle machinery by inducing multinucleate giant-feeding cells surrounded by asymmetrically dividing neighboring cells. Cell cycle activation is a basis for gall induction and maintenance. Giant cell development is characterized by an acytokinetic mitotic phase, followed by an endoreduplication stage leading to polyploidization of nuclei during cell expansion. The endocycle involves genome duplication without cell division, resulting in polyploidy. E2Fa and E2Fb transcription factors are positive regulators of the mitotic as well the endocycle being essential to drive S phase. Via functional and molecular analysis we unraveled the role of AtE2Fa and AtE2Fb for gall growth and development. In situ transcript localization has shown that AtE2Fa and AtE2Fb are highly expressed in these nematode feeding sites. A detailed analysis of E2F knockout and overexpressing lines suggests that despite both genes seem to have slightly different timing and spatial localization during gall expansion, both are essential for gall development.