Israel Lothan made aliyah from Poland in the year 1935, and a year later he enrolled at the Technion in Haifa, where he studied architecture. Due to World War II his graduation was delayed to 1945. After his graduation, Lothan gained an apprenticeship to Le Corbusier in Paris. However, because of the War of Independence, which commenced at the time of his upcoming departure, his plans were cancelled, and he stayed in Israel.
His professional career began in The Prime Minister's Office Department of Planning.
In 1952, He began consulting for The Ministry of Housing in the Department of Planning, and after a year's apprenticeship abroad, began his independent career in Israel.
Lothan Architects won 17 contests, and planned many projects: "Bet Yad Labanim", Tel Aviv (with Zvi Toren), Kiraon and Rimon neighborhoods - Kiryat Ono, winning contests for planning Kikar Hamdeina and Nordia neighborhood (with Aba Elhanani and Oscar Niemeyer), Hall of Judaism Wolyn, Bet Hahayal in Haifa, etc.
Since 1982, he partnered/started working together with his architect son Rami Lothan.