Former NFL star Rob Gronkowski says Apple stock was his best investment ever, turning $69,000 into $600,000

• Former NFL star Rob Gronkowski's said his best investment ever was buying shares of Apple.
• In 2014, Gronkowski invested $69,000 in Apple. He said the investment is worth more than $600,000.
• Apple stock has surged 972% since the iPhone 6 was launched in 2014.

Former NFL star Rob Gronkowski said the best investment move he ever made was buying Apple stock a decade ago.

Gronkowski told Fortune that in 2014 he received the tip from his home builder to buy shares of Apple.

"The guy actually who built my house in Foxborough, he told me, 'Hey buy Apple stock. I'm telling you that's where it's at," Gronkowski said.

"Every time I saw him, when we were building the house, he kept saying, 'Get Apple. Get Apple," Gronkowski said. "So after the 50th time, I got it. And let me tell you, it's the best investment I've ever had in my life."

Gronkowski said he decided to "go big" with his investment. He called his financial advisor and instructed him to buy $69,000 worth of Apple stock, solely based on the advice from his home builder.

At the time, Apple's product roadmap included the iPhone 6, which proved to be a major hit with consumers as it included Apple's first foray into a larger-screen phone, the iPhone 6+. It was also a year before Apple released its first Apple Watch, which debuted in April 2015.

Apple stock is up 972% since the company unveiled its iPhone 6 on September 9, 2014. A $69,000 investment on that date would be worth about $740,000 today. Gronkowski didn't specify the exact date he made his initial purchase of Apple stock.

After about two-and-a-half years, Gronkowski said he completely forgot that he had purchased the shares and was surprised to see it was worth about $250,000. He took some profits and held on to the rest.

"So I sell off the portion of the $69,000 I bought in and I have, now to this date, I have over $600,000 in Apple stock all because of the investment I made in 2014, having no idea what I was doing, but just listening to the guy that built my house here in New England so I appreciate that," Gronkowski said.

Gronkowski was drafted into the NFL in 2010 as the 42nd pick and played for 11 seasons, including nine seasons with the New England Patriots and two seasons with the Tampa Bay Buccaneers.

He is a four-time Super Bowl champion and made about $70 million in his time playing in the NFL.