Tim Ardillo said he was waiting next to his mother's coffin with his young son to be given the Host when the priest said he was not eligible because he was married outside the Church.
The man claims this is not the reason and thinks he was refused because the priest knew he was married to another man.
Revd Mark Beard, of St. Helena Catholic Church in Amite, did not return several calls by journalists from the Baton Rouge Advocate newspaper, which broke the story.
Mr Ardillo said the week after the funeral a quotation from 1 Corinthians was handed out at Sunday Mass.
Highlighted in red ink it said: "Whoever eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of sinning against the body and blood of the Lord.
"A man ought to examine himself before he eats of the bread and drinks of the cup. For anyone who eats and drinks without recognizing the body of the Lord eats and drinks in judgment of himself."
The man said he has since been given an apology by the Diocese of Baton Rouge.
The Catholic Church states its members should not take Holy Communion if they have committed a 'grave sin' for which they have not been to confession about.
In a statement the Diocese of Baton Rouge said: "With respect to the specific matter raised, the Catholic Church expects that any individual Catholic who is in a marital situation which is not in conformity with its doctrines will not come forward to receive the body and blood of the Lord at Mass.
"For Catholics, reception of Holy Communion among other things is an expression of unity with the church's teachings, including those about marriage."
Diocese spokeswoman Donna Carville told the local newspaper the diocese does not condone denial of communion to Catholics just because they are gay.
"That's very surprising that he was denied communion," she said, "that just doesn't happen. ... We don't deny people communion."
She added: "Who are we to judge whether they believe [the church's teachings on the communion] or not? It's between you and God."
Mr Ardillo said he would have abstained from Communion had the priest approached him before the funeral Mass.