The 43-year-old digital entrepreneur said he would leave the show after the current 12th series.
He says he wants "to pursue other interests".
Kelly Hoppen and Duncan Bannatyne are also leaving at the end of this series leaving Peter Jones as the only original investor left on the show. Deborah Meaden is also staying.
Piers Linney said: "After hearing over 200 pitches and made nine deals, I have had a fantastic experience on Dragons' Den.
"I feel honoured to have had the opportunity to contribute to such an iconic and long-running TV show and to have been the first Dragon with Afro-Caribbean heritage.
"I've really enjoyed it. It has been a great experience and a pleasure to share with millions of viewers the growing importance of digital innovation.
"It is now the right time for me to move on, although entrepreneurship and diversity are two of my greatest passions so I will continue to focus my energies on supporting both.
"I've got many more things I want to do in life that I plan to do - and I've got family as well so time is at a premium."
The married father-of-two joined the show in 2013 alongside Kelly Hoppen.
Linney says he'll continue to work closely with the businesses he's backed, including digital picture book publisher Lost My Name.
His other investments included self-tan brand Skinny Tan, festival and clubbing holidays operator Mainstage Travel and customised trainers company Skribbies.
He also said he wouldn't rule out a return to TV.
He previously appeared in Channel 4's The Secret Millionaire in 2011.
"I might do TV again," he said. "I'm good at being me and if something reflects my interests, it might be something I'm interested in doing."
Dragons' Den continues on BBC Two on Sunday evenings at 21:00 GMT.
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Piers Linney has announced that he is stepping down from BBC Two series Dragons' Den after two years.