An electrical connector assembly includes a first electrical connector, a second electrical connector and an adapter assembled between the first and second electrical connector. The first electrical connector includes a first insulating housing and a plurality of first contacts received in the first insulating housing. The second electrical connector includes a second insulating housing and a plurality of second contacts received in the second insulating housing. The adapter includes a base and a plurality of pin contacts retained in the base, the pin contacts run through the base and contact the first and second contacts simultaneously.