Born (as Georg Josephthal) in Nuremberg in Germany, Yoseftal was a member of the Yiddisher Yudenbund youth movement in his teens. After high school he studied law and economics at the University of Heidelberg, Berlin, Munich and Basel, gaining a PhD in jurisprudence at the latter.
In 1932, he joined Habonim, and the following year was appoined head of the youth department of the Bavarian Jewish community. He moved to Berlin in 1934, and two years later was elected secretary general of the German branch of HeHalutz. In 1936 he married Senetta Yoseftal, later also an Israeli politician.
Yoseftal made aliyah to Mandate Palestine in 1938, and two months after arriving, he was sent to London to try and save German Jewry. He returned to Palestine in 1939, establishing a work brigade in Ra'anana, which later founded kibbutz Gal'ed in 1945.