Alfredo De Oliveira, a Madeiran native who has been living in Jersey since 2008, pleaded guilty before Assistant Magistrate Peter Harris.
Police legal adviser Susie Sharpe told the court that CCTV images had captured De Oliveira as he pursued the woman.
He followed the 42-year-old victim from the Snow Hill area until she was alone near Devonshire Place, where the assault occurred.
Magistrate Harris declined jurisdiction, moving the matter on to the Royal Court due to its serious nature.
De Oliveira was jailed on remand and is to appear in the Royal Court on August 15.
He will also be immediately placed on the registered sex offenders list.