Barnard was born in Carterton, a town in the Wairarapa region. He studied law at Victoria University of Wellington, and became a lawyer in 1908. He eventually settled in Te Aroha, where he served on the Borough Council. In 1915, he travelled to the United Kingdom and joined the Royal Army Medical Corps to serve in World War I. After serving for a time in Egypt, he became a gunner in the Royal Field Artillery, serving in Palestine. Following World War I, he returned to New Zealand and resumed practice as a lawyer.