Born in Porto Empedocle, Sicily, Camilleri saw his works turned into a TV series in 1999 that was picked up in Britain, the United States and Australia.
"I love him and I hate him. I owe him practically everything, he opened the door for the other books," Camilleri said about Montalbano in an interview with Italy's La Stampa newspaper.
"But he's invasive, pretentious, unpleasant and when I encounter a problem, I can see him turning up telling me 'I'd do it like this'," said the writer known for his overflowing ashtrays.
Camilleri is reported by Italian media to have given the last novel in the detective series to his editor in 2006, with instructions that it be published only after his death.
It is not known how the novel wraps up the tale of the gruff but straight-arrow Montalbano, or the police colleagues who help him uncover truths in a murky world of Mafia alliances, omerta, prostitution and drugs.
Camilleri said he owed a "huge debt" to Belgian writer Georges Simenon's detective Jules Maigret, but Montalbano takes his name from Catalan novelist Manuel Vazquez Montalban, creator of gastronome detective Pepe Carvalho.
Also a theatre and television director and scriptwriter, Camilleri published his first Montalbano novel "The Shape of Water" in 1994 when he was 69 years old.
- 'Not afraid of death' -
He died in a Rome hospital after a period in intensive care. His funeral is expected to be private.
"I am not afraid of anything, not even of death. I have had a fortunate life," he said in a recent interview.
"If I could, I would end my career seated in a square, telling stories".
The author's passing sparked an outpouring of grief and messages of love from across Italy, with everyone from anti-Mafia journalist Roberto Saviano to migrant rescue charities and the country's state police paying their respects.
Malta's Prime Minister Joseph Muscat Tweeted his farewell to "a genius from a nearby island".
"Goodbye to Andrea Camilleri, father of Montalbano and tireless narrator of his native Sicily," Italy's deputy prime minister Matteo Salvini said on Twitter.
Camilleri was politically-engaged, never shying away from criticising those in power.
He was no friend of Italy's far-right strongman, regularly denouncing him for his Italians-first campaign and recently saying "the consensus around Salvini reminds me of the one around Mussolini".
- Blindness 'boosted memory' -
Camilleri has sold some 20 million books in Italy, and his Montalbano novels have been translated into about 30 languages.
The writer was known for often mixing Sicilian dialect with standard Italian.
"Let's say I invent one percent of the words but the rest comes from the dialect of Sicilian farmers or workers," Camilleri told AFP in an interview.
Camilleri, who published his first novel aged 57, also had a long career in moviemaking and radio.
"I am blind, but losing my sight made all my other senses come back to life," he said in 2017.
"They have come to the rescue. My memory has improved, and I remember more things than before with great lucidity, and I still write."
A young Camilleri enrolled in 1944 for a degree in literature and philosophy in Palermo, but never graduated.
He went on to study at the 'Silvio d'Amico' national drama school in Rome, which launched him into directing and writing.
He would become the first to direct a Samuel Beckett play in Italy.
Married in 1957 with Rosetta Dello Siesto, he had three children: Andreina, Elisabetta and Mariolina.
Asked in 2018 what would make him happy, he replied: "if the ceiling opened up and down came a man who said 'I am William Shakespeare, and I really like your Montalbano'".