The fourth and fifth series will each run to 12 episodes, airing in Autumn 2010 and Autumn 2011 respectively.
Show creator and executive producer Russell T Davies, who left as showrunner on Doctor Who earlier this year, will remain in the role on both new series of SJA.
Nikki Wilson, producer on series three, has been promoted to executive producer, while Torchwood's Brian Minchin has joined the team as a producer.
"We are thrilled to be making many more episodes of The Sarah Jane Adventures," said CBBC controller Damian Kavanagh. "It has been a huge ratings and critical success on CBBC and we hope our viewers are going to be hooked on Sarah Jane's action-packed adventures for some time to come."
The fourth series, which begins filming in Cardiff later this month, sees regulars Tommy Knight (Luke), Daniel Anthony (Clyde) and Anjli Mohindra (Rani) return alongside Elisabeth Sladen (Sarah Jane).
Adversaries in the new run of episodes include the Nightmare Man and the Shansheeth, while the gang will travel to an alien world for the first time and take a "dangerous journey back in history".
Series four writers include Phil Ford, Joseph Lidster, Rupert Laight, Gareth Roberts and Clayton Hickman.