Unlike the Protestant Churches, several high-profile Australian Catholic leaders opposed conscription.

The major spokesperson for Catholic anti-conscription sentiment was Daniel Mannix, who became Archbishop of Melbourne in 1917.

Mannix first announced his opposition to conscription in late 1916, shortly before the first referendum, but his most famous speech on the subject was made in Brunswick in January 1917, at the opening of St Ambrose’s School.

There are several reasons why the Catholic Church was different: they were closer to working class and Labor politics. Sympathy for the question of Irish Home Rule was also a significant factor, although responses to this question were complex.

Many Australian Catholics enlisted in the Australian army. Nonetheless, many Protestant Australians accused Australian Catholics of disloyalty to the British Empire, and considered them to be suspect. Anti-Catholic cartoons and other campaign materials were common. In this regard, the conscription referendum campaigns worsened the often difficult relationships between Protestant and Catholic Australians.