An electrical connector includes an insulating body, a first installation module and a second installation module. The first installation module includes a first internal circuit board and a first terminal adapter block. The second installation module includes a second internal circuit board and a second terminal adapter block. The first internal circuit board and the first terminal adapter block include first fool-proof portions that cooperate with each other. The second internal circuit board and the second terminal adapter block include second fool-proof portions that cooperate with each other. The first fool-proof portions are different from the second fool-proof portions, thereby preventing the first terminal adapter block from being incorrectly connected to the second internal circuit board, and preventing the second terminal adapter block from being incorrectly connected to the first internal circuit board. The present disclosure also relates to an electrical connector assembly having the electrical connector.