After graduating from Princeton in 1952, Abernethy went to work at NBC News. He was assigned to the network's Washington, D.C. bureau in 1953 and spent two years there before being transferred to London. He returned to Washington in 1958 to report and anchor network news updates. From 1961 until 1963 Abernethy hosted a weekly television news magazine for NBC, "Update", which targeted teenagers and young adults. He also anchored the network's coverage of the Northeast blackout of 1965 from its Washington news bureau.