The 31-year-old described hearing the news as "dream moment" and has vowed to give everything if given an opportunity to represent Australia against England this summer.
He told reporters: "The last four years here in Australia, I couldn't wait to be a citizen, especially in the field of cricket. I want to give back something to this country.
"I will try my best to be a good citizen and I will do my best for this country. It was a tough time for me these last four years but it's worked now and I have an opportunity to prove myself, to prove my skills especially in cricket and hopefully as the best citizen of Australia.
"It is a dream moment for me. I spoke to my friends so many times, it is time to enjoy and hopefully I will deliver better than fast here."
Ahmed will now join the Australia A squad on a tour of South Africa next month, following successful completion of the final formal requirement - an official citizenship ceremony.