Mr McLetchie's son James McLetchie told mourners at yesterday's ceremony: "The thing that I am most proud of my dad has nothing whatsoever to do with his political career. I am most proud of the simple fact that I genuinely regarded my father as one of my best friends."
Mr McLetchie said his father "effectively reached the top of his profession in Scotland" when he became leader.
He also paid tribute to the "remarkable" way he rebuilt his life after the death of his first wife, Barbara.
"He simply refused to let the tragedy of my mum's death destroy our family, and for that alone I owe him everything."
He spoke of being in the same church, St Columba's in Blackhall, Edinburgh, as a 13-year-old for his mother's funeral after her death from cancer 20 years ago, recalling his father saying it was hard but they would have to get on with life.
He spoke of his friendship with his father as they played golf and followed Hearts, and when reflected on his loss and repeated his father's advice, the Kirk burst into spontaneous applause.
Mr Fergusson spoke of a point in Scottish Tory history when the party might not have recovered had it not been for someone of the talent, strength and determination of David McLetchie arriving on the scene.
Mr Fergusson described the ex-Conservative leader as having been "warm, humorous, engaging, hospitable and immensely entertaining".
But Mr McLetchie also "possessed a steely determination to do what he believed was right, whether it was popular or not, whatever difficulties that belief might cause him". He took on a monumental task on becoming Scottish Conservative leader and recovered from the expenses row which forced his resignation to emerge as an even greater figure.
The Lothian MSP died from cancer last week at the age of 61.
Scottish Tory leader Ruth Davidson and her Labour and Liberal Democrat counterparts respectively, Johann Lamont and Willie Rennie, also attended.
Bankrupt former Scottish Tory treasurer Malcolm Scott also made a rare public appearance. He was formerly one of the party's biggest donors, putting in £1.6m over five years.
Former Labour Chancellor Alistair Darling, chair of the Better Together campaign to keep Scotland in the UK, and Foreign Secretary William Hague were also in the congregation.