Mr Farron has not yet announced if he will go for the top job, but in a joint statement Willie Rennie and Kirsty Williams said he is "an inspirational leader".
The Liberal Democrats are looking for a new leader after Nick Clegg resigned in the wake of massive losses following Thursday's General Election.
Tim Farron has said he is a "committed Christian" and told the Huffington Post his faith "matters massively".
"It speaks to the foundation of who and what I am. It also gives me peace because I know this isn't everything," he said.
The Scottish leader, Willie Rennie, joined Kirsty Williams, the party's leader in Wales, in urging him to stand.
Mr Farron is a "committed liberal, a brilliant communicator, an outstanding campaigner and an inspirational leader," the pair said.
The statement added: "Thursday's results were devastating for the Liberal Democrats.
"Despite our loss, our party remains optimistic, hopeful and confident about what we can achieve on behalf of Britain.
"To move forward we need a fresh start. With that in mind, we call on Tim Farron to stand to be our next federal leader.
"We believe he is the right person to rebuild our party, inspire and lead us into next year's election campaigns. We will wholeheartedly support him if he decides to put himself forward.
"With him as leader we can show that we are a compassionate, tolerant, internationalist, reformist party that looks beyond sectional interest to the greater good, to our children's future not just ours, that believes in partnership home and abroad, not division, that is liberal and democratic.
"We urge Tim to step up and lead our party to recovery."