They have three children, Philip, Penny, and William Jr.[1][dubious – discuss] Caldicott and her husband moved to Boston, Massachusetts, in 1966 and she entered a three-year fellowship in nutrition at Harvard Medical School.

Her early achievements included convincing Australia to sue France over its atmospheric testing of nuclear weapons in the Pacific in 1971 and 1972, which brought the practice to an end.

[3] After visiting the Soviet Union in 1979 with an AFSC delegation and upon learning the impending US deployment of cruise missiles (which would end arms control) and Pershing II missiles that could hit Moscow from Europe in 3 minutes,[4] Caldicott left her medical career to concentrate on calling the world's attention to what she referred to as the "insanity" of the nuclear arms race and the growing reliance on nuclear power.

[5] Caldicott stood as an independent candidate for the Australian House of Representatives at the 1990 federal election, contesting the Division of Richmond, against the Leader of the National Party, Charles Blunt.

Regarding Caldicott's book Nuclear Power is Not The Answer, he wrote: "The scarcity of references to scientific papers and the abundance of unsourced claims it contains amaze me.

"[10] Also in 2011, Caldicott made a written submission regarding the Darlington Nuclear Generating Station new build project in Canada in which she asserts that plutonium can cause cancer of the testicles after accumulation in these organs.

[13] In 1992, Caldicott received the 1992 Peace Abbey Courage of Conscience Award at the John F. Kennedy Presidential Library in Boston for her leadership in the worldwide disarmament movement.

[19] A 2004 documentary film, Helen's War: Portrait of a Dissident,[20] provides a look into Caldicott's life through the eyes of her niece, filmmaker Anna Broinowski.

The 2013 documentary Pandora's Promise also features footage of Caldicott, interspersed with counter-points to her assertions regarding the health impacts of the Chernobyl nuclear disaster.