YouthNet, which provides online advice and support, and Get Connected, which provides a telephone helpline for people aged under 25, said they hoped the move would enable them to increase their joint reach from 1.7 million young people last year to two million by 2018.
A spokeswoman for the charities said the move was a natural step forward given that the two organisations, which each employ 24 people, had said they would work together more closely after the collapse of the anti-bullying charity BeatBullying last year.
If the merger proceeds as planned, it is expected that the charities will form a new organisation at about the turn of the year and launch a new charity in the spring, the spokeswoman said.
She said it was too early to say whether there would be any redundancies as a result of the merger.
"It looks likely that there will be some restructuring, so there might be redundancies, but the number of staff that are likely to be affected is expected to be small," she said.
The new organisation will be led by Chris Martin, chief executive of YouthNet.
Jessica Taplin, chief executive of Get Connected, will be joining the volunteering charity vinspired as chief executive early next year, it was announced today.
Because of the merger, YouthNet will leave its central London office and move in to Get Connected’s two locations, which are also both centrally located in the capital.
Martin said: "By combining YouthNet’s digital reach and expertise with Get Connected’s excellent one-to-one telephone support service, we can offer young people a recognisable, safe and trusted place to turn whenever they need it.
"Demand from young people for support has never been greater, and we believe our new charity will help to fill the gap where statutory services have been withdrawn and smaller organisations for young people have shut down."