Montgomery began her long journalism profession as a cub reporter for Waco-News-Tribune while receiving her education at Baylor University (1930—1935). Later she graduated from Purdue University (1934) and began work as a reporter on the Louisville Herald-Post.

In 1943, she became the first female reporter in the Washington bureau of the New York Daily News, and embarked on her extensive Washington DC career. She covered notable foreign affairs (the Berlin Airlift among them), was a syndicated columnist for Hearst Headlines and United Press International and was a well-read correspondent with the International News Service.

At Franklin D. Roosevelt's funeral, Montgomery was the only female of the 12 invited reporters. In 1950, while a reporter for the New York Daily News, she was voted president of the Women’s National Press Club. In 1959, she was a member of then Vice-President Nixon’s press corps on his tour of Russia. Montgomery wrote of her 25 years covering Washington in her 1970 book, “Hail to the Chiefs; My Life and Times with Six Presidents”.

Montgomery wrote annual newspaper columns listing predictions by psychic Jeane Dixon beginning in 1952. In 1962, “Once There was a Nun: Mary McCarran's Years as Sister Mary Mercy” was published and thus began Montgomery’s long career as a non-fiction author. In 1965 her book, “A Gift of Prophecy” about Jeane Dixon was published and became a best-seller, selling over 3 million copies.

Montgomery retired from her journalism career in 1969. As part of their Texas Collection, the Archives Division at Baylor University contains a research collection which include papers of Montgomery.

In her book A World Beyond, Montgomery revealed that in a past incarnation she had been alive during the time of Christ and known as Lazarus' third sister Ruth, who is not mentioned in the Bible.

Echoing the earlier predictions of Edgar Cayce, Montgomery believed that ancient advanced civilizations of Mu and Atlantis had destroyed themselves thousands of years in the pre-history of modern man. Montgomery claimed we would see remnants of the lost continent of Atlantis rise from the sea after a "Polar Shift".

Montgomery predicted in the 1970s (allegedly with the help of her spirit guides) that World War III would begin in the mid-1980s when a brush-fire war, started by Ethiopian strongman Mengistu Haile Mariam, would spread first to the Middle East, and then Europe. Montgomery's "Guides" allegedly stated quite clearly that humans have free will and can make their own decisions regarding their destiny, and during the late 1970s and early 1980s, in fact changed the future, preventing the war.

Montgomery also predicted in the 1970s and 1980s, that America would have a "walk-in" as president in the 1990s, ("unsure which term, 1992 or 1996") before the Polar Shift, which was to happen "in the last months of the century" as it seemed to "the Guides."

In the late 1990s, the Guides predicted in her 1999 book, The World To Come, that the walk-in president would not come until 2008 at the earliest, and therefore the Shift would be delayed until 2010-2012 at least. The potential catastrophe of the shift was also reduced by human free will. Except for Florida and the coast of California, the Guides reported, most of America will survive.

Montgomery was a prolific writer on the subject of clairvoyance, reincarnation, past life regression, psychic phenomena, and clandestine extraterrestrials, most of which were sold as popular mass market paperbacks.

Once There was a Nun: Mary McCarran's years as Sister Mary Mercy (Putnam, 1962)

Mrs. LBJ (Avon, 1964)

A Gift of Prophecy: The Phenomenal Jeane Dixon (William Morrow & Company, 1965) first appeared in a condensed version as story in Reader's Digest entitled "The Crystal Ball" (July 1965).

A Search for the Truth (William Morrow & Company, 1967)

Flowers at the White House (1967)

Here and Hereafter (Coward, McCann & Geoghegan, 1968)

Companions Along the Way (Coward, McCann & Geoghegan, 1970)

Hail to the Chiefs: My Life and Times with Six Presidents (Coward, McCann & Geoghegan, 1970)

A World Beyond: A Startling Message from the Eminent Psychic Arthur Ford from Beyond the Grave (Coward, McCann & Geoghegan, 1971)

Born to Heal: The Astonishing Story of Mr. A and the Ancient Art of Healing with Life Energies (Coward, McCann & Geoghegan, 1973)

Companions Along the Way (Coward, McCann & Geoghegan, 1974)

The World Before (Coward, McCann & Geoghegan, 1976)

Strangers Among Us: Enlightened Beings from a World to Come (Coward, McCann & Geoghegan, 1978)

Threshold to Tomorrow (Putnam, 1983)

Aliens Among Us (Putnam, 1985)

Ruth Montgomery: Herald of the New Age (Fawcett, 1987)

The World to Come: the Guides' Long-Awaited Predictions for the Dawning Age (Harmony, 1999)