In the video, the priest was seen performing the mass at the Paroisse Saint Maron before the church begins to rattle and the lights go off.
The church's stained glass windows smashed on the ground as the priest ran for cover safety.
The camera fell after the blast and shattered glass could be seen spread across the floor.
The blast was the most powerful ever to rip through Beirut, a city still scarred by civil war three decades ago and reeling from an economic meltdown and a surge in coronavirus infections.
It sent a mushroom cloud into the sky and rattled windows on the Mediterranean island of Cyprus, about 100 miles away.