Rodger Hill said his family is “broken” after the sudden death of David Hill, 30, on Saturday.
He said on Twitter: “I can’t believe I’m writing this. My amazing son David passed away today playing rugby in Dublin for the Scottish Parliament.
“He was the best and the pain is unbearable. We are broken.”
David Hill, who was described as “rugby daft”, worked as the head of office for Scottish Tory MSP and Holyrood justice spokesman Jamie Greene.
He was playing for the cross-party Holyrood team in a match against Dail and Seanad XV when he died.
While a post-mortem examination will establish the cause of death, it is understood that it may be due to a head injury and heart complications.
Mr Greene described him as a “friend, colleague and confidant for so many in the Scottish Parliament over the years”.
He said Mr Hill “loved his politics, but he loved his rugby more”, and added: “The whole parliament, my party and the whole rugby community is deeply saddened by this awful news today, and our condolences lie entirely with his family, friends and colleagues.”
Mr Hill’s death prompted tributes from across Holyrood, with Scottish First Minister Nicola Sturgeon tweeting: “This is so terribly sad. My deepest condolences to David’s family, friends and colleagues.”
She said Mr Hill’s teammates are “all deeply shocked and heartbroken”.
Scottish Conservative leader Douglas Ross said: “Our whole party is shocked and saddened by David’s tragic passing. He was a kind, generous, well-liked and highly respected part of our team.
“We will all miss him dearly. All our thoughts are with his family and friends.”
Holyrood Presiding Officer Alison Johnstone said: “Words can’t express how shocked and saddened all at the Scottish Parliament feel on learning of David’s sudden death.
“My thoughts and those of all @ScotParl are with David’s family, friends and colleagues at this difficult time.”
In a statement, Scottish Rugby said: “We are shocked and saddened by David’s passing today.
“Described as ‘rugby daft’ by his family, David played for Dumfries Saints and was a regular at Scotland internationals.
“The condolences of everyone at Scottish Rugby go out to his family and friends at this time.”