His second Irish-language collection, Banana, was published by Cois Life in 1999, and won Gradam Uí Shúilleabháin /Irish Book of the Year Award.
In 2005 his selected short stories were published by Cois Life under the title Úlla (Apples).
One of them, entitled Gealach (Moon), was published by Leabhar Breac in 2012 and won an Oireachtas prize.
In 1992 the Abbey Theatre produced The Winter Thief/Gadaí Géar na Geamhoíche in English and Irish on alternate nights, using the same cast.
A selection of his work can be heard on the audiobook Niall Tóibín ag léamh gearrscéalta le Seán Mac Mathúna (Niall Tóibín reading short stories by Seán Mac Mathúna) (Cois Life, 2009).