Raja Yoga contains transcripts of lectures by Vivekananda on "Raja Yoga", his interpretation of Patanjali's Yoga Sutras, and a "rather free translation" of Patanjali's Yoga Sutras plus Vivekananda's commentaries, which also was a series of talks. It presents Vivekananda's understanding and interpretation of Patanjali's Yoga Sutras, "and a selection of hathayoga teachings on the basis of the beliefs that he shared with his students." These included elements from traditional Hinduism, but also ideas from Western science, Idealism, and "the Neo-Vedantic esotericism of the Brahmo Samaj and Western occultism," including mesmerism and "American Harmonial religion".

Vivekananda adapted traditional Hindu ideas and religiosity to suit the needs and understandings of his Western audiences, who were especially attracted by and familiar with Western esoteric traditions and movements like Transcendentalism and New Thought. An important element in his adaptation of Hindu religiosity was the introduction of his four yoga's model, which includes raja yoga, his interpretation of Patanjali's Yoga Sutras, which offered a practical means to realize the divine force within which is central to modern Western esotericism. The other three yogas are the classical karma yoga, bhakti yoga, and jnana yoga.

Vivekananda's interpretation of Patanjali's Yoga Sutras is mostly based on the part on astanga yoga, the eight limbs of yoga described in the Sadhana Pada or practice part. According to De Michelis, Vivekananda's ideas on raja yoga mainly consists of two different models, with sometimes a third "mode of thought".