Investigators say Dr Denis Furtado carried out the procedure on Lilian Calixto at his home in Rio de Janeiro but she fell ill during the procedure.
Dr Furtado took her to a hospital where her condition worsened and she died some hours later, police said.
He then disappeared and a judge has issued a warrant for his arrest.
Dr Furtado, 45, has appeared on Brazilian television and has nearly 650,000 followers on his Instagram account.
Ms Calixto, a 46-year-old married mother of two who worked in banking, had travelled from her home in Cuiaba, central Brazil, to undergo buttock enhancement by Dr Furtado on Saturday evening, reports said.
The procedure, believed to involve the injection of acrylic glass filler, took place at his apartment in the upmarket district of Barra de Tijuca.
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