One demonstrator was arrested in Jugon-les-Lacs, a commune in the Cotes-d'Armor region where some 700 people had gathered earlier in the day.
A security camera was torched and some protesters pelted police, who responded with tear gas.
Demonstrators chanted slogans against France's Socialist government, which earlier this month suspended the application of the so-called ecotax.
"People struggle to pay their bills at the end of the month, and now we're going to ecotax them" said one protester, pretending to strangle himself.
There were more anti-tax protesters elsewhere in Brittany and also around the country, including near the major cities of Lyon and Marseille, and in the capital Paris.
The ecotax, aimed at encouraging environmentally friendly commercial transport, imposes new levies on French and foreign vehicles transporting commercial goods weighing over 3.5 tonnes.
It has came under fire from farmers and food sector workers across the country, but especially in Brittany, where the economy is heavily dependent on agriculture.
Faced with the unrest, the government decided to suspend the new levy at the end of last month. Then on Friday, it announced more than one billion euros in emergency funds for Brittany, among other measures.
But protesters are still not pacified and a large scale rally is planned for November 30th.