Dodd grew up around politics—his father was a four-term U.S. representative (1953–57) and senator (1959–71)—and began his own public service at an early age. He joined the Peace Corps after graduating from Providence College in Rhode Island in 1966 and spent two years working in the Dominican Republic. He served in the U.S. Army, first in the National Guard and later in the reserves, from 1969 to 1975. In 1972 Dodd received a law degree from the University of Louisville in Kentucky; the following year he was admitted to the Connecticut bar and opened a private practice in New London. Dodd was elected to the first of three terms as a U.S. representative in 1974, the midterm election bringing a large influx of Democrats to Congress during ongoing investigation into the Watergate Scandal. Following his father's career path, Dodd ran for and was elected to the Senate in 1980. He was reelected in 1986, 1992, 1998, and 2004—the first Connecticut senator to be elected to five consecutive terms.

Dodd's time in Congress was marked by an interest in child welfare, fiscal reform, and education. He served on the Senate's committees on banking, housing, and urban affairs (chair from 2007); foreign relations; health, education, labour, and pensions; and rules and administration (chair 2001–03). In 1995–97 he served as general chair of the Democratic National Committee. In January 2007 Dodd announced that he planned to pursue the 2008 Democratic presidential nomination. His bid for the presidency never garnered widespread public support, and he withdrew from the race after finishing sixth in the Iowa Democratic caucus in January 2008.