In 1851 he served as an apprentice winemaker for Agoston Haraszthy and then John Patchett before establishing his own winery.

Krug married Carolina Bale, the daughter of early Napa Valley pioneer and miller Edward Turner Bale and granddaughter of María Isidora Vallejo of the prominent Californio Vallejo family, on December 26, 1860.

[1] Krug was inducted into the Culinary Institute of America's Vintner's Hall of Fame in 2007.

[2] The dowry Bale left for her included 540 acres (2.19 km2) of land north of St. Helena, California, on which Krug planted a vineyard and founded his winery in 1861.

The winery still exists, and is owned by Robert's younger brother Peter Mondavi's family.