Fashion students from Hawick High Schools wore their own designs for the annual Tartan Day parade in Manhattan.
Mr Mather joined them for event, which brought this year's Scotland Week celebrations to a close.
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Hide AdThousands of pipers and drummers paraded through the city, with Holyrood Presiding Officer Alex Fergusson leading the procession after being made Grand Marshal of the event.
Mr Mather said: "It was a proud honour to join the fashion students from Hawick High School, whose exceptional talent and skills will support Scotland's future economic growth, at the annual Tartan Day parade."
Mr Fergusson said he was "especially delighted" to be given the role of Grand Marshall for this year's parade. It was a "genuine honour to lead the parade in celebration of all things Scottish".
The parade is the culmination of a week of Scotland-themed events in New York to celebrate Scottish-American Heritage.
These included the 10k Scotland Run in Central Park and a Whisky Live event celebrating whisky. Last Monday a host of celebrities took to the catwalk at the annual Dressed to Kilt fashion show. They included rugby star Thom Evans, X Men actor Alan Cumming, Hollywood funnyman Mike Myers, and Sex And The City's Kyle MacLachlan.