The 14-year-old boy and another protester were shot dead in the western city of Barquisimeto on Tuesday night.
The local governor blamed armed government supporters. Two students were killed during protests last week.
Nicolas Maduro's presidency has come under increasing pressure as the economy suffers and opponents accuse him of creating a dictatorship.
Mr Maduro was pelted with objects by angry protesters as he left a military event in the south-eastern state of Bolivar earlier on Tuesday.