Irish president Michael D Higgins, DUP leader Sir Jeffrey Donaldson, former Taoiseach Bertie Ahern and Sinn Fein vice president Michelle O’Neill also attended the service in Lambeg.
Nobel Peace Prize winner Lord Trimble died last week at the age of 77 following an illness.
The former leader of the Ulster Unionist Party played a key role in forging the 1998 Good Friday/Belfast Agreement that ended decades of conflict in Northern Ireland.
Months after the deal was signed, the peer, from Co Down, was jointly awarded the Nobel prize with late SDLP leader John Hume in recognition of their efforts to stop the bloodshed and establish a power-sharing system of devolved governance in the region.
On Tuesday, the Stormont Assembly will reconvene for a special sitting to pay tribute to Lord Trimble.
The institutions are currently on ice, with the DUP blocking the creation of a power-sharing administration in protest at Brexit’s Northern Ireland Protocol.
Lord Trimble’s widow, Lady Daphne, took her place in the front row as the coffin was carried into the church by their sons and daughters.
Minister Rev Fiona Forbes welcomed mourners to the service.
She said: “The array of those who have gathered today to pay their respects bears witness not only to David’s impact on the political landscape of which he was so much a part, but also to the imprints he left upon the same, and to the legacy he left all of us.
“Of course, we come to remember an academic, a party leader, a peacemaker, a Nobel laureate, the first to serve in the role of first minister in the new Northern Ireland Executive established as part of the Good Friday Agreement.
“But we also come to remember a husband, father, and grandfather, a brother, brother-in-law and uncle, a colleague, a committed member of this church family, and a friend.”
Lord Trimble’s eldest son, Richard, has thanked the public for their sympathies and kind words following the death of his father.
Rev Dr Charles McMullen told mourners that Lord Trimble’s actions had allowed a generation in Northern Ireland to grow up in “relative peace”.
Delivering a tribute at the service, the former moderator of the Presbyterian Church said: “Alongside others, he rose to seemingly impossible challenges with considerable strength of character, intellectual acumen, and complete integrity.
“The reward for all of us has been a radically changed landscape here in Northern Ireland, which has saved many lives and allowed a generation to grow up in relative peace.
“As so many have said over these past few days, history will be exceedingly kind to David even if life brought many unrelenting pressures and demands.”
Dr McMullen added: “He was a committed family man and, as I have sat with Daphne, his daughters Victoria and Sarah, and sons Richard and Nicholas over these past few days, I have been deeply touched and moved by so many stories, all of which underlined how dearly loved he was by them.
“They gave him to us and we want to take this opportunity to express our deepest appreciation to them.”
He told the congregation the Omagh bombing had doubled Lord Trimble’s determination to achieve peace.
Dr McMullen said: “As first minister, David had to cut short a family holiday in order to get home to visit Omagh in the aftermath of that terrible bombing which killed so many, an experience that left him utterly devastated, but doubled his determination to keep building bridges and working for peace.
“I can remember bumping into him days after the conclusion of the Good Friday Agreement and hearing how, afterwards, on his way home he had gone to a hole in the wall but could not remember his pin number.
“That was an indication of being under almost unbearable stress, but then he always had the courage of his convictions and was prepared to pay the cost.”
Dr McMullen said he hoped the funeral service could be used as an inspiration to redouble efforts to resolve political differences in Northern Ireland.
Referring to Lord Trimble’s Nobel prize speech in 1998, he told mourners: “In that speech, David made this inspiring comment: ‘The dark shadow we seem to see in the distance is not really a mountain ahead, but the shadow of the mountain behind – a shadow from the past thrown forward into our future. It is a dark sludge of historical sectarianism. We can leave it behind us if we wish. But both communities must leave it behind, because both created it’.
“It is a very powerful quotation because it reminds us of the achievements of the Good Friday Agreement in placing the principle of consent at the centre of our politics and ultimately removing the gun.
“It reminds us also that, although we are on a journey from the past, the mountain still casts a shadow and we are all, to a greater or lesser extent, recovering sectarians.
“Can we use this service today, in a fitting tribute to one of the great, to redouble our efforts on this island home of ours?
“With courage, pragmatism and generosity of spirit, may our politicians engage wholeheartedly in resolving the outstanding issues surrounding the Northern Ireland Protocol, so that our democratic institutions are quickly restored and we can all move forward together.”