McCaffrey was born in Cambridge, Massachusetts on April 1, 1926. During the first year of her marriage, she began to write science fiction.  In 1970, she and her three children moved to Ireland.

McCaffrey says that she is “opinionated, asocial, extroverted, and impossible.”  She has learned to be “proud of being different.”   But she adds,  “It isn’t easy!  It’s lonely until you realize that you have inner resources that those of the herd mentality cannot enjoy.  That’s where the mind learns the freedom to think science-fictiony things, and where early lessons of tenacity, pure bullheadedness, can make a difference.  Most people prefer to be accepted.  I learned not to be.”