 Harald Nielsen was born in Frederikshavn and started his footballing career in hometown club Frederikshavn fI, where he debuted in the second-highest Danish league in March 1959.From his position of center forward, Nielsen finished the top scorer of the league as Frederikshavn won promotion to the Danish football championship.In the top Danish league, Nielsen debuted for Frederikshavn against Boldklubben Frem in March 1960.