What MAFS' Timothy didn't want viewers to know until after the show.

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Married At First Sight's Timothy Smith has disclosed a criminal past that he is "not proud of".

Appearing on A Current Affair, Timothy confirmed that he previously spent time in multiple United States super-maximum prisons for drug smuggling — a detail he hid from MAFS producers.

Watch: Meet MAFS bride Lucinda. Post continues below.

"I was a helicopter pilot in North America that did something really stupid, and made a decision to fly marijuana across the Canadian border into the US, and got caught doing it," he said.

"It's something I'm not proud of. I'm definitely not proud of it, but it doesn't define who I am and I'm not the same person I was 17 years ago."

The reality star was first introduced to drug trafficking during a pre-paid helicopter flying lesson in Canada, where he was identified as a natural. 

He was responsible for transporting marijuana from Canada to the US, and took part in over 20 drug-smuggling flights, earning $100,000 for each job.

"I'd meet a 4WD and land behind it and within a minute the helicopter would be loaded with marijuana and I'd fly south into the US," he said.

"It was $100,000 a trip for a couple of hours of work."

However, it all came crashing down when he was apprehended by US Immigration and Customs Enforcement agents upon returning to Los Angeles.

Following his arrest, Timothy pled guilty to drug trafficking and was required to spend one year in jail.

"I'm sorry for what I did. I'm sorry to everyone I hurt. But I don’t want anyone to do what I did," he said.

"That decision in 2006 keeps affecting me. Unfortunately or fortunately it shapes who I am today. 

"Someone threw some money at me and said, 'Go and take a lesson tomorrow'. I did, and the instructor said I was a natural. That was the beginning of the end."

While in prison, the MAFS groom faced several personal tragedies, including losing his mother and brother shortly after one another.

"My world changed. I was shipped off to a federal facility. No guards, four walls, 180 guys, good or bad," said Timothy.

"If I could go back and change it, I would. There’s no question I’d change it. 

"I wasn’t there when my mother and brother died. I paid the price. I pay the price every day."

Timothy is now sharing his story hoping to prevent others from making the same mistakes he did, emphasising the severe consequences of his actions.

"I did something very stupid, and I paid the price. I paid the ultimate price," he said.

Feature Image: Nine/A Current Affair.