Sheikh Mohammad Osseiran began his theological studies at a seminary in Tyre, Lebanon. He then moved to Najaf, Iraq, to pursue advanced studies at the major seminaries there. Sheikh Osseiran was a student and follower of the late Grand Ayatollah Abu al-Qasim al-Khoei.
Sheikh Osseiran remained in Najaf until Iraqi dictator Saddam Hussein started pressuring the non-Iraqi Shi"a scholars to leave the country.
Sheikh Osseiran is also a member in the SISC. Sheikh Osseiran is married to Doctor Zeinab Dirani-Osseiran. Sheikh Osseiran was born in Saida, the largest city in South Lebanon, and ancestral hometown of the Osseiran family, to Hassan Osseiran, a feudal landlord, and Aminah Osseiran, a homemaker. Sheikh Osseiran is known to be an opponent of the ideology.
Sheikh Osseiran is the trustee of the Husseiniyah of Sidon.
After leaving Najaf, Sheikh Osseiran returned to his hometown and was entrusted with the running of the Husseiniyah of Saida by an edict from Grand Ayatollah Khoei.
