Viewing figures consistently rose culminating in almost 2.5m hits for the first week online and 2.6m hits during the second week.
'Sofia's Diary' is aimed at teenagers and twenty-somethings. It follows the adventures of 17-year-old Sofia Taylor and her friends as she adjusts to her new life in London.
Fans are encouraged to interact with the show and contribute to storylines. Each week viewers decide which way Sofia should turn regarding an important decision in her life, with their vote determining the outcome.
Sarah Gavin, Bebo's global communications director, said: "We are absolutely thrilled to reach the five million mark during the all important launch weeks of 'Sofia's Diary'.
"The unique interactive element of the series encourages viewers to return daily to see if their individual vote has changed the next episode's outcome, giving fans a complete 360-degree personal experience."
Each weekday, Sofia and her friends update their video diaries with two- to three-minute instalments, as well as their own Bebo profiles.
Users can stay in touch with Sofia via mobile phone by receiving daily updates from her during the day, which lets them know what's happening in her world. The service is free to all users in the UK regardless of network and can be activated by texting "Sofia" to 60505.