Franciscan University of Steubenville in Ohio posted a series of ads to Facebook to promote its online theology, catechetics and evangelisation programs on Good Friday.
However, Steubenville's web communications director Tom Crowe reported on the school's blog that one of the ads, which pictured Jesus on the cross, was rejected.
Facebook's reason for blocking the ad stated: "Your image, video thumbnail or video can't contain shocking, sensational, or excessively violent content."
The blog post continued: "The San Damiano Cross. Jesus in glory, reigning from his cruciform throne. This is what the monitors at Facebook consider excessively violent, sensational, and shocking.
"And indeed, the Crucifixion of Christ was all of those things. It was the most sensational action in history: man executed his God.
"It was shocking, yes: God deigned to take on flesh and was "obedient unto death, even death on a cross."
Crowe told Fox News he doesn't know why only the one clearly depicting the San Damiano Cross was blocked.
"It may have been the algorithm or a low level staffer who has something against Christianity," he added.
Facebook has recently apologised for rejecting the advertisement and admitted that it made a mistake. It has since officially approved the ad.
A Facebook spokesperson told Fox News: "Our team processes millions of ads each week, and sometimes we make mistakes.
"This image does not violate our ad policies. We apologise for the error and have already let the advertiser know we approved their ad."
Crowe told Fox News the San Damiano cross is very important to the Franciscan order because it is believed God spoke to St. Francis through this cross.
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