Theodore (Teddy) Kollek was born in Nagyvázsony, 120 km from Budapest, Hungary as Kollek Tivadar. His parents named him after Theodor Herzl. The family moved to Vienna in 1918. Growing up in the Austrian capital city, Kollek came to share his father Alfréd's Zionist convictions.
Teddy Kollek (second from the right), with the Ein Gev Pioneers (1934–39)
In 1935, three years before the Nazis seized power in Austria, the Kollek family immigrated to British-controlled Mandatory Palestine. In 1937, he was one of the founders of Kibbutz Ein Gev, on the shore of Lake Kinneret. That same year he married Tamar Schwarz. They had two children, a son, the film director Amos Kollek (born in 1947), and a daughter, Osnat.
In the 1940s, on behalf of the Jewish Agency (Sochnut) and as part of "The Hunting Season" or "Saison" Teddy Kollek was the Jewish Agency's contact person with the British Mandate MI5, providing information against right-wing Jewish underground groups Irgun and Lehi (known as "Stern Gang"). He succeeded Reuven Zaslani and preceded Zeev Sherf in this function, and was carrying out the Jewish Agency's policy of assisting the British in fighting these groups. In 1942 Kolleck was appointed the Jewish Agency's deputy head of intelligence. Between January 1945 and May 1946 he was the Agency's chief external liaison officer in Jerusalem and was in contact with MI5's main representative as well as members of British Military Intelligence. On 10 August 1945 he revealed to MI5 the location of a secret Irgun training camp near Binyamina. Twenty-seven Irgun members were arrested in the raid that followed.
During World War II, Kollek tried to represent Jewish interests in Europe on behalf of the Jewish Agency. In 1947–48, he represented the Haganah in Washington, where he assisted in acquiring ammunition for Israel’s then-fledgling army. Kollek became a close ally of David Ben-Gurion, serving in the latter’s governments from 1952 as the director general of the prime minister’s office.