An electrical connector includes a first contact module and a second contact module adjacent the first contact module. Each contact module has a plurality of ground and signal contacts. Each ground contact and signal contact includes a mating portion, a mounting portion, and an intermediate portion extending between the mating portion and the mounting portion. In each contact module, the intermediate portions of the ground contacts are disposed in a first common plane and the intermediate portions of the signal contacts are disposed in a second common plane that is spaced from the first common plane. The first contact modules and the second contact modules are arranged such that two adjacent signal contacts of the first and second contact modules, respectively, define a differential signal pair such that the intermediate portions of the adjacent signal contacts are spaced more closely than the intermediate portions of two adjacent ground contacts of the first and second contact modules, respectively.