Yitzhak was born on July 15, 1921 in Izmir, Turkey, to Aharon Mordechai and Sarah. The family made aliyah in the 1920s illegally, taking a ship to Beirut, then smuggled by way of Rosh HaNikra via Nablus to Jerusalem.
They then moved to Neve Zedek in Tel Aviv. His father worked in the film industry, representing Paramount Studios.
At first, he attended the Alliance School, then the commercial high school in Tel Aviv. In 1935, when he was fourteen, he joined the right-wing Hagana, and in 1937, he joined IZL. When the split occurred, he followed Yair. Since his father was a supporter of the underground, the command staff often met in his house, including Yair. After Yair’s murder, Lehi was paralyzed for a time, until Shamir broke out of Mizra and reorganized the underground. Then they began training again with firearms, and Yitzhak took a basic course in Segula, led by Tzefoni. He then went on attacks against various British targets, throwing grenades at the gate of Sharon, attacking Major Harris, ambushing British forces by Tel HaShomer, and others. Later, he joined Department 6, the Intelligence Department. They always had a weapons cache in their home.
After the State was established, Yitzhak and his comrades joined the IDF in May 1948, serving in Company A of Battalion 82, 8th Brigade. He fought in all the battalion’s battles. After the Battle of Auja el-Hafir, he was sent to a national communications course, where he served until the end of the war.
In 1944, he married Fania Zipporah Teitel (whose father was a pediatrician), and the couple had two daughters.
The Masri brothers set up a travel agency. In 1970, Yitzhak travelled to New York and set up a travel agency there. In 1991, he returned. He was a Likud member and he painted as a hobby.