Jacobus Stephanus Cellier, son of Jan Cellier and his wife Magdalena, was educated at the South African School of Mines, which was associated with the South African College, Cape Town. He passed the first and second mining examinations of the University of the Cape of Good Hope in 1897 and 1898, but ill health prevented him from preparing for his mine description in 1899. In 1900 he passed the university's Survey Certificate examination (through the South African College). Proceeding to Johannesburg for practical training he was awarded the Diploma in Mining Engineering in 1902 and admitted as a land surveyor in 1903. Subsequently he was employed by the General Mining and Finance Corporation, Consolidated Gold Fields of South Africa, and the Johannesburg Consolidated Investment Company as mine manager at Nigel Deep, Robinson Deep, and Sub Nigel. In 1909 he married Plestina Frances Quinton, with whom he had two daughters.
In 1913 Cellier was appointed professor of mining and surveying at the South African School of Mines and Technology (later the University of the Witwatersrand) in Johannesburg, despite his lack of a university degree. He held this post to 1920. At some time in his career he worked also as a draughtsman in a consulting engineering office.