Pillsbury became actively involved in politics when he worked on the presidential campaign of Democrat Eugene McCarthy in 1968 in New Hampshire. This surprised some because his father George was a Republican state senator and was actively supporting Richard Nixon.
Pillsbury ran for United States Congress as a Green Party candidate in Connecticut's 3rd congressional district in 2002. He received 9,050 votes, for 4.9% of the total vote.
Pillsbury is Co-Chair along with Alison Duncan of the Green Party's Dispute Resolution Committee.