He was born on 24 May 1870, at the family farm, Bovenplaats, near Malmesbury, in the Cape Colony. His parents, Jacobus Smuts and his wife Catharina, were prosperous, traditional Afrikaner farmers, long established and highly respected.
Jan was quiet and delicate as a child, strongly inclined towards solitary pursuits. During his childhood, he often went out alone, exploring the surrounding countryside; this awakened a passion for nature, which he retained throughout his life. As the second son of the family, rural custom dictated that he would remain working on the farm; a full formal education was typically the preserve of the first son. However, in 1882, when Jan was twelve, his elder brother died, and Jan was sent to school in his brother's place.