The 48-year-old actor was initially hesitant to discuss the procedure before he could see that it was working - but John insists he doesn't feel "ashamed" at all.
The wrestler-turned-actor - who has been married to Shay Shariatzadeh since 2020 - told Extra: "I just wanted it to work.
"It worked. I went into (Dr Anderson) with significant hair loss, and he not only taught me how to take care of myself, to keep the hair that I have healthy, the treatments that I do every day, he also helped me move some of the hair up here, put it up here, and man, I feel great about it.
"I'm not ashamed to say it."
Cena has encouraged other men to consider undergoing the same procedure.
The Hollywood star also admitted it had helped to increase his confidence and boost his career.
"It was a single-day process. It's available and accessible. And I just preach if you're one of the seven of 10 out there, there are options for you, and you're not alone … It's not for everybody, but it certainly was for me," he said.
"And even just the aesthetic confidence is one thing, but man, I want to entertain audiences and the variation of a hairstyle, you can become a different character.
"I viewed it as also a good work opportunity for me. So there are multiple reasons why I wanted to lean in. And again, I made the choice. I'm confident with the choice. I'm not ashamed of what I did at all."
Cena recently admitted he wished he had his hair transplant a decade ago.
The WWE star underwent the procedure on his thinning locks last November and lamented the "shame" he previously felt around the treatment.
"I hate the fact that if there wasn't so much shame around it, I'd have gotten it done 10 years ago," he told People.
"I thought I was alone, but seven or eight out of 10 (men) suffer from thinning or baldness."
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