The Russian-born star, who switched allegiances last March, confirmed on Saturday her citizenship had been granted ahead of her first Australian Open as a local.
"Officially an Australian," Kasatkina wrote on Instagram.
"Happy, Grateful and Free."
She added to the media: "Honestly, I cannot even describe how much that means, because it's not just about the passport. It's about the acceptance, let's say.
"Because honestly, like, the whole process, the support from the people, from the other citizens - it's been amazing.
"I couldn't imagine that, coming from the completely different background to receive this amount of support basically from strangers.
"I felt so much love, honestly ... but now that I'm fully Australian, I'm just super-proud and grateful. I mean, that's a responsibility, but that's what I was looking for.
"I'm just really grateful. I mean, I don't know if I will be ever able to pay back the same amount what this country gave me."
Kasatkina, 28, experienced a taste of the Australian crowd's support in short campaigns in Brisbane and Adelaide.
The former world No.8 will embrace her first home slam when she opens her campaign against Czech teenage qualifier Nikola Bartunkova.
"This is a good pressure, so I would choose this one compared to what I have been through in the past couple of years," she said.
"... Let's call it a fun pressure, I don't know.
"Also for the first time I'm gonna play in front of such a big home crowd, so that's gonna be special. Definitely have to manage my nerves, because ... (I've) never been in this situation before.
"But honestly I'm super proud, and it's (an) extremely positive change."
World No.48 Kasatkina hasn't returned to Russia since coming out as gay in a video interview in 2022, when she also became one of few Russian-born athletes to speak out against the war in Ukraine.
She received criticism for switching allegiances and has experienced social media abuse.
Kasatkina is happy to trade those pressures for getting to grips with Australian slang and a culture based around "give it a crack" and relaxing over a coffee.
"Coming with my background, everything, it's about pressure, sacrifice, but in some ways, survival as well," she said.
"This calm way of thinking, it's actually something I'm missing."
Kasatkina believes her game is already in a better place than last year, when she was "mentally exhausted" and took a break.
"Most importantly, mentally I'm much, much better," she said.
"So that's the most important thing, because ... especially at the end of last year, the last season was very, very tough. I was trying to get out of this, like, hole basically. It's never easy.
"But, yeah, I'm really happy with the progress I have done, and now is just about competing well and just about tennis, which is basically what I was looking for for quite a time.
"... That's why I wrote "grateful and free," because finally I can just breathe. I can live and just do my job and not to be worried about the things which are not in my control."
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