Phillips was born to william Cornelius Phillips of Juniata, Pennsylvania and Mary Catherine Savino of Ripacandida, Italy. He is of Italian descent on his mother's side and of Welsh descent on his father's side. His parents moved to Camp Hill (near Harrisburg, Pennsylvania) in 1959, where he attended high school and graduated valedictorian of his class. He graduated from Juniata College in 1970 summa cum laude. After that he received his physics doctorate from the Massachusetts Institute of Technology. In 1978 he joined NIST.
Phillips married Jane Van Wynen shortly before he went to MIT. Neither had been regular churchgoers early in their marriage. However, in 1979, they joined the Fairhaven United Methodist Church in Gaithersburg, Maryland because they appreciated its diversity. He is a founding member of the International Society for Science and Religion. He and his wife have two daughters; Caitlin Phillips (b 1979) who founded Rebound Designs, and Christine Phillips (b 1981) who works in Science Communication.
He is one of three well-known Scientists and Methodist laity who have involved themselves in the religion and science dialogue. The other two Scientists and fellow Methodists are Chemist Charles Coulson and 1981 Nobel laureate Arthur Leonard Schawlow.
In 1996, he received the Albert A. Michelson Medal from The Franklin Institute.
In Oct 2010 Phillips participated in the USA Science and Engineering Festival's Lunch with a laureate program where middle and high school students got to engage in an informal conversation with a Nobel Prize–winning scientist over a brown-bag lunch. Phillips is also a member of the USA Science and Engineering Festival's Advisory Board.
During a seminar at the UMCP Department of Chemistry and Biochemistry titled Coherent Atoms in Optical Lattices Phillips stated, "Rubidium is God's gift to Bose–Einstein condensates."
