Dave - who fronts the weekend breakfast slot and is also a Channel 4 face - will join co-presenter Lisa Snowdon on the show from January.
Johnny quit the popular programme abruptly last month after almost eight years. Listeners were told of the new appointment this morning.
Dave has been a breakfast host for 95.8 Capital FM's sister station XFM and is well-known as a presenter for Channel 4's youth strand T4. He first found TV fame presenting MTV's afternoon show TRL.
Dave, who is engaged to Sugababe Heidi Range, said: "To be given the opportunity to wake up London every weekday morning is a dream come true on so many levels.
"I have an absolute passion for radio, I love this city and of course it's no bad thing working alongside the gorgeous Lisa Snowdon. Bring it on."
Johnny took over the breakfast role from Chris Tarrant who had famously presented it for almost 17 years. After four years as a solo host he was first joined by his old Big Breakfast colleague Denise Van Outen in 2008 and then Lisa stepped in later that year.
Richard Park, director of broadcasting for Capital's parent company Global, said: "Dave Berry is a massive radio talent, and has already proved himself a huge hit with Capital listeners.
"I am convinced that the chemistry between him and Lisa Snowdon will make for great radio and that the show will become a must-listen for London every weekday morning."