The trio, who play Rhys Lawson, Andrew Robinson and Sophie Ramsay respectively, will depart screens in 2013.
Neighbours confirmed the news on the show's official Twitter page today (November 26) after the departures were reported in TV Week magazine.
Asked whether the three cast members are leaving, a representative replied: "Yes they are. We'll miss those guys!"
Meanwhile, Jones told her online fans: "Im both sad but excited :D Hope you get to see me on your tv screens again soon. :)"
Jones joined Neighbours as Sophie in 2009, while Smith took over the role of Andrew later that year.
Barber, meanwhile, was cast as Rhys in May 2011.
Other recent cast changes at Neighbours have seen Jordy Lucas film her final scenes as Summer Hoyland, while Valentina Novakovic is bowing out as Natasha Williams.
Neighbours airs weekdays at 1.45pm and 5.30pm on Channel 5 in the UK, and weekdays at 6.30pm on Eleven in Australia.