Bishop Walsh, 90, died last Wednesday at his residence in Ennis.
In his words of welcome, the Bishop of Killaloe, Fintan Monahan, relayed a message of condolence from the Vatican on behalf of Pope Francis.
The Cathedral of Saints Peter and Paul in Ennis was full to capacity for the requiem mass of Bishop Walsh.
Friends and relatives, including his many nieces and nephews, were in attendance alongside figures from the world of politics, sport, and the Catholic Church.
President Michael D Higgins was represented by his Aide-De-Camp Col Stephen Howard.
Mayor of Clare Alan O'Callaghan was also in attendance with senior members of Clare County Council.
Mourners said Bishop Walsh was a "people person" whether teaching maths and physics in St Flannan's College and coaching the hurling teams, or becoming parish priest of Ennis and going on to be Bishop of Killaloe.
Speaking on their way into the cathedral, Miriam Burke and Emma Kirby said their uncle was the youngest of six, all predeceased.
"We are the last link to Willie and we're so upset at his passing," said Miriam, "but overwhelmed by all the love and all the stories we've heard in the past week, and hearing what he means to everybody".
Emma Kirby agreed: "We were so lucky to have him as part of our family but he is treasured right across Clare and beyond. He was the kindest and most gentle human being who did so much for the downtrodden and marginalised."
Concelebrants at the funeral mass include Archbishop Kieran O'Reilly of Cashel and Emly, Bishop Ger Nash of Ferns, Fr Laurence Walsh OCSO of Our Lady of Silence Abbey Roscrea along with other bishops and priests in attendance.
A message from Apostolic Nuncio to Ireland Archbishop Luis Mariano Montemayor was read out at the start of the funeral mass.
"His Holiness Pope Francis was saddened to learn of the death of Bishop Emeritus William Walsh, and he sends condolences to you, the clergy, religious and lay faithful of the Diocese of Killaloe.
"Recalling with gratitude the kind and gentle way with which he carried out his many years of episcopal ministry, His Holiness commends the late Bishop’s soul to the mercy of Christ the good shepherd, to those gathered for the Mass of Christian burial and to all who mourn his passing, in the sure hope of the resurrection, the Holy Father imparts his blessing as a pledge of consolation and peace in the Risen Lord."
Music for the Liturgy was led by the cathedral choir, including members of the Forever Young Choir, of which Bishop Walsh was a founding member.
In his funeral homily, Bishop Monahan referred to cineáltas chríost (the gentleness of Christ) which was the Episcopal motto of Bishop Walsh.
"During the week we were busy praying for the health and recovery of Pope Francis. While we were doing that a pastor cut out of the same cloth as the Holy Father stole away with no warning and less fuss.
"Willie Walsh died as he lived, getting on with the business of things, not hanging around, just moving on with intent and clear direction."
Bishop Monahan spoke of his kindness and care for the poor, the marginalised, people struggling and suffering in life.
"He did this through his unstinting work with the Traveller community, his pastoral outreach to survivors of abuse, the sick, the vulnerable, so many who availed of his spiritual outreach as a true pastor of Jesus Christ," Bishop Monahan said.
There were some funny stories as well including the challenges of hearing loss faced by both bishops.
He said: "On a recent trip in the car we had an interesting experience, with me driving, obviously on the right and Willie being on my left.
"He was deaf in the right ear and me in the left. Nonetheless, we had a delightful journey, with much talk and neither of us having much of a clue what the other was saying."
As a bishop, he said Bishop Walsh showed pastoral leadership empowering lay people and improving the role of women in the Church. He challenged the system.
He said: "Willie was a radical in the true sense of the word. He challenged unquestioned beliefs, the accepted mores of society and in doing so stripped them back to their origin, measuring them up against what he believed was the core of the Gospel, cineáltas chríost, the gentleness of Christ.
"Being frequently out-spoken, he stirred things up. This sometimes ruffled feathers, was occasionally misunderstood, upset a few and others saw it as an effort to overturn hard earned orthodoxy.
"However, Willie, often in thinking out loud did this with raw honesty, integrity, conviction and belief that his exploration, questioning was a legitimate response to arriving at the divinely revealed truth using the gifts that God generously bestowed upon us."
During reflection the Bishop's grandnieces Lucy and Sophie Kirby sung 'A Mhuire Mháthair’.
Bishop Walsh was buried in the grounds of Ennis Cathedral following the funeral mass.