He was educated in York, in the Royal School of William and Mary in the Horse Fayre, which cost no money to attend. Guy Fawkes, Edward Oldcorne and brothers Christopher and John Wright were among Tesimond's classmates, all of whom would become involved in the Gunpowder Plot. In 1580, at the age of seventeen, he entered English College in Rome. After three years of philosophy, Tesimond, with permission from the Jesuits' cardinal protector, Giovanni Morone joined the Society of Jesus in April 1584.