Hasan Esat Işık was born in Istanbul. His father was Mehmet Esat, a well known physician.[3] After graduating from Galatasaray High School and Ankara University Faculty of Law, he held various positions in Ministry of Foreign Affairs. He served as the Permanent Representative of the European Office in Geneva in 1952, and as Ambassador to Brussels, Moscow and Paris from 1962 to 1973.[4] Following the military coup of 27 May 1960 which ended the rule of Democrat Party (DP) Işık, Oğuz Gökmen and Semih Günver who were close to Fatin Rüştü Zorlu, minister of foreign affairs in the DP cabinet, were dismissed from the Ministry.[5] When they were cleared of all charges as a result of the investigations, they were appointed to new positions, and Işık was named as the ambassador of Turkey to Belgium.[5]
Hasan Esat Işık was also the deputy secretary general of the CHP. He was among those who were banned from politics for 5 years by the new constitution following the 1980 coup d'etat.
Işık died in Ankara on July 2, 1989 at the age of 72.