Hacham Shimon Abecassis was born to Mas'ouda and Hacham Shlomo in 1859, in Mogador, Morocco.
He initially studied and taught Torah in Mogador. In 1931 he moved to Casablanca, where he studied and taught at the Keter Torah yeshiva, under the auspices of Mr. Yitzhak Maliakh, who saw to all his needs. When he returned to Mogador, he officiated as a dayan at Hacham Abraham Ben Soussan's Beit Din.
Hacham Shimon Abecassis married Freiha, and the couple had both sons and daughters.
Hacham Shimon Abecassis passed away on 17 Nissan, 5719 (1959). He is the author of Peleg Mayim – sermons and Ach Tov LeIsrael – original commentary on the Talmud and Responsa, both published in London in 1906, and of Sass Anochi – sermons and original commentary on the Bible and Rach VeTov – original commentary on the Talmud, published in Casablanca in 1937.