Moina was a talented artist and joined the Slade School of Art at the age of fifteen. The Slade was known for encouraging young women in the Arts at the turn of the nineteenth century. Moina was awarded a scholarship and four merit certificates for drawing at the School. It was at the Slade in 1882 that Moina met her friend Annie Horniman, who would become the major financial sponsor for the Matherses, as struggling artists and occultists, in backing the Hermetic Order of the Golden Dawn.
Moina met her husband, Samuel Liddell MacGregor Mathers, in 1887, while studying at the British Museum where Samuel was a frequent patron. A year later, her future husband founded the Hermetic Order of the Golden Dawn, one of the most influential organizations in the Western Mystery Tradition. Moina was the first initiate of this Order in March, 1888. Her chosen motto in the Golden Dawn was ‘’Vestigia Nulla Restrorsum’’ meaning “I leave no traces behind.” A year later in 1890, she married S.L. Mathers and Mina Bergson became Moina Mathers. In their occult partnership, her husband was described as the "evoker of spirits" and Moina as the clairvoyant "seeress" who often illustrated, as an artist, what her husband “evoked”. In March of 1899, they performed the rites of the Egyptian goddess Isis on the stage of the Theatre Bodiniere in Paris.
In 1918, when her husband died, Moina took over the Alpha et Omega, a successor organization to the Golden Dawn, as its Imperatrix.