Featuring Zeffirelli's signature lush photography, Brother Sun Sister Moon was conceived and executed in much the same visual manner as his Academy Award-winning adaptation of Romeo and Juliet (1968). Brother Sun Sister Moon attempts to draw parallels between the work and philosophy of Saint Francis and the ideology that underpinned the worldwide hippie movement of the 1960s and early '70s. The film is also known for the score composed by Riz Ortolani.
Clare, a young woman also of a wealthy family, serves and cares for lepers of the community. Francis is inspired by her example, and in return, after his community forms, she comes to join the brothers in their life of poverty.
The film contrasts Francis's innocence, piety and virtue with the bloated pomp of official Roman Catholic Church doctrine, which is depicted as being weighed down by internal politics, corruption and hypocrisy. Much of Brother Sun Sister Moon was filmed in locations and buildings frequented by the real-life Francis of Assisi.
In 2004, Donovan re-recorded the songs from the long out-of-print soundtrack. Brother Sun, Sister Moon was released exclusively on iTunes Store.