"For women you had to wear blouse, slacks, dress or skirt - for men it was slacks, button-down shirt, tie, suit jacket. And it panicked me," Whisman said.
"At that point, I didn't identify as transgender but I had to stop and think 'why am I having these feelings? Why am I having these thoughts?' and I realised, shoot, I'm having this panic moment because I don't want to choose a female uniform because that's not who I am, I'm not female."
Whisman said it seemed like such a little thing, but it can be a big deal to some.
"I didn't grow up saying 'I'm a boy' but deep inside, that identity was in me," he said.
"When I decided to transition, one of the things I did think about was 'how am I going to do this?'
"When you're different, when there's something about you ... it's gossip fodder. I didn't want that."
He was worried about losing his job and how it would affect his permanent residence status.
Whisman met with the bank's head of human resources at the time, and over the course of a day came out to over 100 people.
He said the new policy meant people no longer had to hide who they really are.
"When you normalise gender diversity, you embrace the experiences of everyone - you say to them 'you know what? That's fine, your experience is fine, your experience is as valid as my experience'," he said.
The change was made following feedback from the bank's staff Pride network of Lesbian, Gay, Bisexual, Transgender, Intersex, Queer and Asexual and other diverse orientations (LGBTIQA+) people, an ANZ spokeswoman said.
The policy applies to uniformed staff, which includes roles in ANZ's branch network and specialists in areas such as Business Banking, Commercial and Agri and Wealth.
"Building a culture of diversity, inclusion and respect is important to our staff and customers," said Felicity Evans, ANZ general manager talent and culture.
"We want our staff to be true to themselves at work, so this is a step we hope helps them feel comfortable."
