Baer was born in Heidelsheim (today part of Bruchsal), Kingdom of Württemberg to Joseph (1816–1891) and Rosina (née Dreyfuss; 1819–1907) Baer, into a Jewish family. His father worked as private money lender and merchant of animal skins, while his mother was a homemaker. He was the second youngest of five siblings. Baer was educated at the Jewish School of Heidelsheim and completed a banking apprenticeship at Bankhaus August Gerstle in Augsburg from 1883 to 1885.^[2]

In 1886, he became a partner in the private bank Samuel Dukas & Co. in Basel, Switzerland. A position he continued to hold until 1896, when he was deployed by his brother-in-law Ludwig Hirschhorn, to Zürich. He became a partner in Bank Hirschhorn, Uhl & Bär, which existed since 1890, and is the ultimate predecessor of today's Julius Baer Group. Since 1901, the bank bore only his name, and was known as Julius Bär & Co., which became one of the leading Swiss private banks.^[2][3]

He was on several board of directors including Lake Thun railway line, Südostbahn and Oerlikon-Bührle (1908–1922).

In 1891, he married Marie Ulrich (1869–1917),^{[4][page needed]} with whom he had three sons;

• Richard Josef Baer (1892–1940),^[5] mathematician and physicist

• Walter Jakob Baer (1895–1970),^[2] director at Julius Baer
• Werner Baer (1899–1960),^{[citation needed]} director at Julius Baer and art collector (namely exhibited at Kunsthaus Zürich)^[6]

His grandson, Hans J. Baer (1927–2011),^[7][8] was a long-term executive director and president of Julius Baer, who became known through his involvement as a mediator in retrieving Jewish funds in the Volcker Commission in the 1990s.^[9]

• Publications about Julius Baer in the Swiss National Library
• Baer, Julius by Ueli Müller in Historical Dictionary of Switzerland (HLS)