Walter Oppenheimer was born in Berlin. After graduating from high school, he moved to London in the 1930s and worked in retail. There he met Helga Kallman, another native Berliner, who was working as a fashion designer. They immigrated to the United States in 1938 and settled in New York, where they married and continued working in retail. In 1947, Mr. Oppenheimer launched Helga Inc. with his wife, designing suits, dresses, and evening clothes to be sold in specialty stores. He managed the business until the couple sold it in 1986.
On their frequent business trips to Europe to buy fabric, the Oppenheimers began to collect art by Georges Braque, Henri Matisse, Pablo Picasso, and other modern European masters. In the early 2000s, the couple donated several dozen works, primarily drawings, to the Hammer Museum at the University of California, Los Angeles. They also funded an exhibition gallery in the museum that is named in their honor.