He was born in County Westmeath to farmer Thomas Willett Donaldson and Barbara Shafgotch.
The family emigrated to Australia around 1863 and Donaldson worked as a station hand and prospector in northern and central Queensland.
He moved to New South Wales permanently in 1883 to become contractors manager in the construction of the Cootamundra-Gundagai railway.
Having transferred to the seat of Wynyard in 1904, he contested Yass in 1913 as the candidate of the Country Party Association, but was defeated.
The Australian Dictionary of Biography describes Donaldson as "feared and hated by two generations of Aboriginals throughout New South Wales.