He was seriously injured in a railway accident in 1914 and had a slow recovery, but in 1915 became Linnean Macleay Fellow in Zoology at the University of Sydney.

In the same year he published in the Cambridge Zoological series, The Biology of Dragonflies, and he also received the Crisp prize and medal of the Linnean Society of London.

In 1925 he was elected a fellow of the Royal Society, London,[1] and in the following year he published his book on The Insects of Australia and New Zealand, a comprehensive work with many illustrations.

In this year he was awarded the Trueman Wood medal of the Royal Society of Arts and Science, London, and was appointed assistant-director of the Cawthron Institute.

Rohan Rivett described those CSIRO years as follows: 'When the CSIR sought for a man to tackle the huge problems of destruction wrought by insects on the Australian economy one candidate stood out above all others.

After difficult negotiations he was brought to Canberra, made a profound impression on members of both Houses of Parliament in a unique address and was appointed Chief of the Entomology Division of CSIR in March 1928 at a salary higher than that of any other.

Within months Rivett [CEO of CSIR] had resignations pending from almost every scientist who had come into frequent contact with Tillyard.

Finally, after prolonged sick leave had failed to produce any assurance from experts of Tillyard's ultimate recovery, Dr Nicholson ... took over as Chief of Economic Entomology.

[6] In his last years Tillyard was much interested in some work on supposed pre-Cambrian fossils in South Australia which was done in co operation with Edgeworth David.

This was caused by Tillyard writing a predominantly supportive review of Arthur Conan Doyle's book The History of Spiritualism.

[12] In the 18 August 1928 issue of Nature in a paper entitled Evidence of Survival of a Human Personality he presented his observations on Crandon's séance phenomena and his belief in life after death.