His parents were Albert Blehr (1805–1872) and Maren Wilhelmine Ludovica Kathinka Stenersen (1818–1877).

In 1905 he was appointed as County Governor (stiftsamtmann) at Christiania (now Oslo), an office he held until 1921.

On 21 June 1921, Otto Blehr became prime minister and at the same time also chief of the Ministry of Finance.

Both were co-founders of the Norwegian Association for Women's Rights, where his wife later became president.

[6] Otto Blehr was awarded the Grand Cross of the Order of St. Olav in 1898.

[3][7] He was the father of Eivind Blehr, a minister in the Quisling regime in World War II.