The 55-year-old American dentist faced a ferocious backlash in July after it emerged he had slaughtered the much-loved lion outside Hwange National park in western Zimbabwe with a bow and arrow.
But today it was announced that Palmer's hunting papers were in order, meaning that Zimbabwe will not be charging him.
Walter Palmer will not be charged
Environment Minister Oppah Muchinguri-Kashiri told reporters: "We approached the police and then the Prosecutor General, and it turned out that Palmer came to Zimbabwe because all the papers were in order."
Reuters reports that Muchinguri-Kashiri said Palmer was free to visit Zimbabwe as a tourist but not as a hunter - implying he would not receive a hunting permit in the future.
Walter Palmer pictured with Cecil's corpse
Palmer has always maintained that, as far as he was aware, the hunt was legal and he had secured the proper documents.
In July, Palmer released a statement saying: "I hired several professional guides, and they secured all proper permits. To my knowledge, everything about this trip was legal and properly handled and conducted.
"I had no idea that the lion I took was a known, local favourite, was collared and part of a study until the end of the hunt. I relied on the expertise of my local professional guides to ensure a legal hunt."
Palmer was convicted of poaching a bear in the US several years ago.
Two more people still face charges related to Cecil's killing. Both allegedly were involved in using bait to lure Cecil out of his habitat in Hwange National Park so he could be killed.
Theo Bronkhorst, a professional hunter in Zimbabwe, is charged with breaching hunting rules in connection with the hunt in which Cecil was killed.
A game park owner is also charged with allowing an illegal hunt. Both have denied the charges.
Cecil was wearing a GPS collar as part of an Oxford University research project which has been ongoing since 1999.