Catherine Martin said the Green Party leadership has heard the concerns after a number of members left the party yesterday.
She narrowly lost the leadership election to Eamon Ryan, with less than 50 votes between them.
High profile election candidate Saoirse McHugh. and a number of other young greens decided to leave the party yesterday, citing concerns about the programme for government and some members of leadership.
After losing last night's vote, Catherine Martin said the party needed to stay united and said the leadership result shows the party "needs change".
Ms Martin said: "We have heard that our party needs change, structural change to cope with the enormous increase in members and staff.
"And cultural change to unite and heal the divisions which have been caused in recent months."
Ms McHugh announced her departure from the party Twitter before the leadership result and in an interview with the Irish Examiner criticised the party as "toxic".
Thread on leaving the greens:— Saoirse McHugh (@saoirse_mchugh) July 23, 2020
I have left the Green Party. I doubt that’s a surprise to most people.
The reasons I have left are obvious, I joined the greens with the hope of furthering the cause of climate justice..1/
Following the election result, Eamon Ryan said he was "very glad" to be re-elected after a "civil" competition and "very honoured" by the result.
"It's a really close result, numbers are tight, and could've went either way, I will reflect on that," he said.
Mr Ryan received 994 votes to Ms Martin's 946.
A total of 1,950 of 2,923 eligible members voted in ballot, the party turnout was 66.7%, with 10 spoiled votes.