The public RTP television channel said at least 35 people were injured when the tree toppled into a crowd outside a church on the island's southern coast.
The Church of Our Lady of Monte, in a suburb of the capital Funchal, is the site of an annual religious gathering attended by faithful from across the island, according to Madeira's tourism website.
The church is surrounded by tall trees.
RTP said authorities would release an official toll later Tuesday, while the Diario de Noticias da Madeira daily said 10 people had been killed and 15 injured.