Canadian astronaut Chris Hadfield, who is Commander of Expedition 35 at the International Space Station, was wearing a special green jumper, shirt and bow-tie ensemble on Sunday.
He also sent a greeting to those celebrating the Patron Saint of Ireland's day back on Earth as well as posting pictures of Londonderry and its "rugged coast facing the North Atlantic" and Tralee in the Republic of Ireland, which he described as being "nestled in the first green we see after soaring across the Atlantic".
He later tweeted a picture of Donegal, saying it was "one of the many famous places I've only seen from space", before adding orbit snaps of Galway "in the afternoon sun", Cork and Drogheda.
Later, the astronaut shared a picture of Belfast "with visibly green countryside signalling the onset of spring".
His St Patrick's Day finale was a photograh of Dublin, "with her port standing out clearly to photographers in Earth orbit".
But remarkably, Commander Hadfield also managed to record a rendition of Danny Boy in orbit from the habitable artificial base.
"From high above the world, to the Irish everywhere," he said in his introduction, before belting out the traditional song.
The astronaut, who has family in the Republic, has seen the number of followers on his Twitter account rocket as he took charge of the International Space Station earlier this month.
But he doesn't just have a talent for space exploration and photography, it seems.