A Brisbane father has been jailed for a "vicious attack" on a fellow train passenger who was speaking on a mobile phone while sitting near him.

Welder Popani Fala Tovale, 40, faced Brisbane District Court this morning to plead guilty to the grievous bodily harm of student Chernor Hadi Bah.

Mr Bah, 20, was left with a broken jaw, broken left cheekbone and lacerations to his face when Tovale attacked him on a Queensland Rail Citytrain in September last year.

The attack took place shortly after Mr Bah alighted a Beenleigh-bound train at Moorooka, in Brisbane's south.

When Mr Bah began a phone conversation with his father, Tovale accosted him, saying: "Hey, get off the train, you African. Why are you talking on your phone. Get off."