According to Brazilian magazine Veja, Aparecida Schunck, 67, was taken on Friday in the neighbourhood of Interlagos, Sao Paulo with her kidnappers said to be demanding a ransom of 120 million Brazilian reals (NZ$52 million).
The magazine says that the ransom demand is the highest in the country's history.
Schunck is the mother of Ecclestone's third wife Fabiana Flosi who met the 85 year-old at the Brazilian Grand Prix in 2009. The pair married in 2012.
Ecclestone and his family are estimated to be worth over 3 billion dollars by Forbes magazine.
In 2012 it was reported that a dental technician threatened to kidnap his daughter Tamara in a $430,000 plot.
A man from Peckham in London pleaded guilty to the threats which are said to have been made between June 19 and July 2011 and was jailed for five years.
Forbes magazine estimates the net worth of the F1 boss - and family - as $3.1 billion. Born the son of a fisherman in Suffolk, England, Ecclestone built Formula One from a niche sport into a global phenomenon after buying the Brabham Racing team in 1971.