Townsend, who achieved worldwide success with the publication of The Secret Diary of Adrian Mole, Aged 13 3/4 in 1982, died after suffering a stroke on April 10. She was 68.
Actor Stephen Mangan, who played Adrian Mole in a 2001 television adaptation of the character, was among those gathered at De Montfort Hall in Leicester.
There were readings from the author's works and tributes from friends,
Journalist Nicci Gerrard led the service which celebrated the life and works of the author.