Standing at 31.19m (102ft), it has broken the previous record set by Chile in 2008 by 25cm (9.8ins).
Brazilian footballer Cafu placed the last block on the tower, which was built in the parking lot of a shopping centre in Sao Paulo.
Lego sent designers from Denmark for the world record attempt.
The first Lego tower was built in London in 1988 and stood at just over 15m.
Since then 53 cities have built towers in more than 30 countries.