Pritchard was born in Seattle, Washington to Frank, Sr. and Jean Pritchard on May 5, 1925. He attended public schools as a child and attended Marietta College from 1946 to 1947. At the rank of Sergeant, he served in the United States Army from 1944 to 1946 and was president of the Griffin Envelope Company in Seattle from 1948 to 1971. He was a delegate to the Republican National Convention in 1956 that renominated Dwight D. Eisenhower for the presidency. He was elected to the Washington House of Representatives representing Washington's thirty-sixth district in 1958 where he served from 1959 to 1967, being reelected in 1960, 1962 and 1964. In the state house, he worked closely with future U.S. Senators Daniel J. Evans and Slade Gorton. In 1966, he was elected to the Washington State Senate where he served a single term from 1967 to 1971. In 1970 Pritchard, a member of Washington Citizens for Abortion Reform (WCAR), introduced a bill allow abortions in the first four months of pregnancy; it was approved and went to the voters as Referendum 20. The measure was approved statewide by voters in November 1970, making Washington the first state to in which abortion was legalized by a popular vote. In 1970, Pritchard ran for the U.S. House of Representatives to represent Washington's first district, challenging nine-term incumbent Thomas Pelly in the Republican primary. Pelly was renominated, but by a smaller margin than anyone expected .
In 1972, Pelly retired and Pritchard ran for the U.S. House of Representatives again, this time successfully, defeating opponents John Hempleman and Craig Honts in a closely contested election. He was easily reelected in 1974, 1976, 1978, 1980 and 1982, serving from 1973 to 1985. He chose not to run for reelection in 1984. In 1988, he made a successful run for Lieutenant Governor of Washington becoming president of the Washington Senate. He was reelected in 1992 and served from 1989 to 1997.
After the end of his second term as Lieutenant Governor, Pritchard went into retirement and became a board member of TVW, Washington's public affairs network. He died on October 9, 1997 in Olympia, Washington, of lymphoma.
Along with a few of his friends, Pritchard invented the game of pickleball at his house in 1965.