On September 20, 2010, parent company Verizon Communications announced he would be president and COO beginning October 1, 2010, succeeding Ivan Seidenberg.

In June 2018, Verizon announced that McAdam would retire from his role as CEO on August 1, 2018, remaining executive chairman through the end of the year.

McAdam had previously been the CEO for PrimeCo Personal Communications, a joint venture of Bell Atlantic and Vodafone AirTouch.

He was vice president of international operations for AirTouch Communications and a lead technical partner for cellular ventures in Spain, Portugal, Sweden, Italy, Korea and Japan.

From 1983 to 1993, he held various executive titles with Pacific Bell, including area vice president of Bay Area marketing and general manager of South Bay customer services.