The pitch is separate from the BBC's reported review of its ad roster, which includes Abbott Mead Vickers BBDO, DFGW, Red Bee Media and Fallon.
It is understood DFGW has not been invited to pitch for the CBBC brief. The review is being overseen by Helen Kellie, the BBC's head of brand and planning.
A spokesman for the BBC said: "We talk to agencies all the time. We feel it is important that licence-fee-payers know where to find our best content."
CBBC launched in 2002 along with the BBC's other digital children's channel, CBeebies. In July, the BBC reported significant growth in audience share and reach for CBBC. CBBC's audience increased in all homes from 0.3 per cent to 0.4 per cent and increased in multichannel homes from 0.5 per cent to 0.6 per cent.