Harald Sandberg was considered one of the best Swedish skippers of his time. At the 1912 Olympic Games in Stockholm he won bronze in the 6 metres class as helmsman of the yacht Kerstin owned by Daniel Broström (1870-1925), a later Minister for Naval Affairs. They prevailed in the match race for third place against the Sass, also from Sweden. In 1932, he was the helmsman of the Fridolin in the One-Tonne Cup off Sandhamn. Of his own boats, the 6-metre-R yachts Unn I and Unn II were particularly successful.
Like his father, Harald Sandberg worked as a wholesaler in Göteborg. He was married to Fanny Eugenia Lindström.