He left UNB in 1943 to join the Canadian Press in Toronto, where he received basic training in editing and writing for newspapers.

Some of his foreign assignments included South Africa's racial conflict, the erection of the Berlin Wall in 1961, Sweden's welfare state, Israel's in-gathering of Jews and the refugee influx to Hong Kong from Communist China.

While on vacation in New Brunswick in 1965, Nielsen learned that a ratepayers' meeting had voted to expel all 45 Malecite children from a Perth-Andover school—for no more substantial reason than their race.

His reports to the Toronto Star led to national publicity and a second, much larger meeting of rate-payers who voted by a big majority to readmit the children.

Robert Nielsen left the Star in 1978 and moved to the Perth-Andover, New Brunswick area where he continued his career as a freelance writer and pursued part-time studies at the University of Maine at Presque Isle, graduating with a Bachelor of Liberal Studies in 1990.