I am keen to take on a working holiday in Australia but I am afraid that it will have an adverse impact on my career. What should I do?

Life is short, I'd say go for it as most of the times you'll regret the chances you did not take. There's no guarantee that it will not have an adverse impact on your career, but, you have 40 years of career ahead of you, what would a 6 months gap matter in the grand scheme of things? :)

Having said that, you'll also have to be prepared to live with your decisions. Somewhere down the road, you may see your peers getting ahead of you in their careers, and that is okay.

Speaking from the perspective of someone who has 4 years work experience and is currently on a 1-year career break living in the States.

I think you need to first be able to answer these 2 questions:

1. What is the main reason for you to go on working holiday?

2. What do you want to achieve in the future (career, finance/wealth, family)?

Given the common sentiment of YOLO, more and more people are tempted by such "opportunities" (in parenthesis because it really depends on what would you like to get out of it) but you may also have realised that most people "choose to stay" and that is because most people have a stronger reason for the second question, which could be "I want to get promoted as fast as I can", "I want to earn as much money as I can to e.g. settle down", "I need to provide for my family", etc. It is not wrong or irresponsible to go on a working holiday but just remember, any decision you make on this (or anything) should be align with your goals. If your goal is to advance fast in your career, the answer should be clear that being away from your job is a no-go. Consider carefully what you want to get out of the working holiday and what value does it add to you.

That aside, you should:

a. Check your company's policy on sabbatical leave

b. Understand whether you qualify for it

In your case, you will be working. You should check whether your company allows you to work while on sabbatical (or would they consider it as moonlighting). Please also understand that just because you have the approval from the management to take sabbatical leave doesn't mean that your position in the company is reserved for you. In the event where they find you redundant to the team or they need the resource but you are not there, your company has every right to displace you (i.e. you are fired).

Sabbatical leave is also granted to people with valid reason (e.g. health issues) and also to people whom the company values. This brings us back to Question 1 that you have to answer. If your reason is "not valid" (what you wish to get out of it does not add value), you don't get the approval and you've basically highlighted to your boss of your wavering commitment to the company. Likewise, if your performance at work is only average, they may not grant you with the approval. The worst case scenario is either they grant you the approval but find a replacement to displace you or they don't grant you the approval but make life difficult for you to make you leave on your own accord.

You did not mention if this is your first job but assuming that you are at a relatively early stage of your career, be mindful that 1 year gap, even a 6 months gap, can be rather disadvantageous. If you don't mind lagging behind your peers in terms of career and wealth (Question 2) and you think it will add great value (Question 1), your path towards working holiday is clear :)