In 1936, aged 21, he attended the World Congress of Faiths at the University of London, heard D. T. Suzuki read a paper, and afterwards was able to meet this esteemed scholar of Zen Buddhism. Beyond these discussions and personal encounters, Watts absorbed, by studying the available scholarly literature, the fundamental concepts and terminology of the main philosophies of India and East Asia.
Watts's fascination with the Zen (or Ch'an) tradition—beginning during the 1930s—developed because that tradition embodied the spiritual, interwoven with the practical, as exemplified in the subtitle of his Spirit of Zen: A Way of Life, Work, and Art in the Far East. "Work", "life", and "art" were not demoted due to a spiritual focus. In his writing, he referred to it as "the great Ch'an (or Zen) synthesis of Taoism, Confucianism and Buddhism after AD 700 in China." Watts published his first book, The Spirit of Zen, in 1936. Two decades later, in The Way of Zen he disparaged The Spirit of Zen as a "popularisation of Suzuki's earlier works, and besides being very unscholarly it is in many respects out of date and misleading."
Watts married three times and had seven children (five daughters and two sons). Watts met Eleanor Everett in 1936, when her mother, Ruth Fuller Everett, brought her to London to study piano. They met at the Buddhist Lodge, were engaged the following year and married in April 1938. A daughter, Joan, was born in November 1938 and another, Anne, was born in 1942. Their marriage ended in 1949, but Watts continued to correspond with his former mother-in-law. In 1950, Watts married Dorothy DeWitt. He moved to San Francisco in early 1951 to teach. They began a family that grew to include five children: Tia, Mark, Richard, Lila, and Diane. The couple separated in the early 1960s after Watts met Mary Jane Yates King (called "Jano" in his circle) while lecturing in New York. After a difficult divorce he married King in 1964. The couple divided their time between Sausalito, California, where they lived on a houseboat called the Vallejo, and a secluded cabin in Druid Heights, on the southwest flank of Mount Tamalpais north of San Francisco. Some regard Watts as having been an unfaithful husband and a poor father.