Dunn returned to Victoria in 1886 and went into private practice. As a result of one of his reports the coalfield at Korumburra, Victoria, was developed. Dunn was appointed director of the geological survey of Victoria in 1904, and in 1905 was awarded the Murchison Medal by the Geological Society of London. Dunn used the award money to publish his monograph on Pebbles, which appeared in 1911. Dunn was elected President of the Royal Society of Victoria in 1906. He retired from the Geological Survey of Victoria in 1912, but kept up his interest in his subject through an energetic old age.