Both players are eligible to play for the Caribbean island through their grandparents and are set to make their debuts in the World Cup qualifiers against St Kitts & Nevis on the 13th and 19th June.
Speaking Millwall's official website, Ifill said: "It's great to be called up for the first time and I'm really looking forward to going.
"I try to keep up to date with the football in Barbados, but it can get a bit tricky over here in England because there isn't much coverage in the press.
"I think all that will change during the next couple of weeks though with these World Cup qualifiers!"