Lodge's initial interest in Spiritualism came from his research into science; after years of researching electromagnetism he became convinced that psychic and spiritual phenomena could exist beyond the range of the average human senses.
He served as President of the Society for Psychical Research for several years.
In 1915 Lodge's son Raymond was killed in action in WWI. Lodge began to attend regular seances and kept detailed records and transcriptions of the messages that were given from his son Raymond. These were published by Lodge in his most famous book, Raymond, or Life and Death. The book contained descriptions of the afterlife in the spirit world, as well as pieces of evidential mediumship collected through Lodge's research.
Lodge's good friend, Sir. Arthur Conan Doyle wrote that with the event of WWI there was an immense increase in the interest of Spiritualism due to the massive loss of lives brought on by the war, and that several works of Spiritualist literature were produced in the aftermath to bring solace and comfort to those who had lost family members. He commented that "The greatest of these books is "Raymond." Sir Oliver Lodge is so famous a scientist and so profound a thinker that his brave and frank avowal produced a great impression upon the public."
The book was a major success and was incredibly popular among Spiritualists, however it was met with some criticism as some felt that the descriptions of the spirit world were too simplistic and not spiritual enough, such as a remark delivered by the spirit of Raymond who stated that he and other soldiers that had passed into spirit were enjoying whiskey and cigars in the spirit world.
Sir Oliver Lodge went on a lecture tour of the United States and arrived in Rochester March 11, 1920. He arrived early in the morning from Cleveland, OH. Lodge gave a lecture at the Convention Hall (now the Geva Theatre) in the afternoon, giving a lecture on "The Evidence for Survival." After returning to England, Lodge joined Doyle in assisting Rochester Spiritualists to fund and plan for the monument to Spiritualism to be erected in 1927.
He and his wife retired to Normanton Manor in South West England not far from Stonehenge. He passed away August 22, 1940 at age 89 and was laid to rest in the parish Church of St. Michael.