He first visited Japan as a medical officer on HMS Coromandel in 1863. For three years he was at Yokohama in charge of medical facilities there. During this time he was in contact with Japanese doctors and culture, and also Ernest Satow who became a lifelong correspondent and friend. He began publishing English translations of Japanese classical works at this time. He left his naval position, returned to England and tried some career choices, but came back to Japan in 1871, having in the meantime married and been called to the Bar. He built up a legal practice in Japan. He was also widely involved with the Yokohama community, with botany, and journalism.
Dickins was especially interested in ferns which he collected at Yokohama and Atami, 1863–65. He sent both living plants and drawings back to J.D. Hooker at the Royal Botanic Gardens at Kew. 
He returned to England in 1879. After spending some further time practicing law in Egypt, he mostly devoted himself to Japanese studies and administration in the University of London.