Barberier is located some 17 km (11 mi) north-west of Vichy and some 17 km (11 mi) north by north-east of Gannat. Access to the commune is by the D36 road from Étroussat in the west which passes through the centre of the commune and the village and continues east to join the D2009 east of the commune. The D183 comes from Bayet in the north and also passes through the centre of the commune, intersecting the D36 at the village, continuing south to join the D66 south of the commune. Apart from the village there are the hamlets of Les Varennes in the south, La Grange Neuve in the east, and Bompré in the north.
The Sioule river flows north along the south-eastern border of the commune and continues north to join the Allier north-east of Contigny.
In 2013 the commune had 133 inhabitants. The evolution of the number of inhabitants is known from the population censuses conducted in the commune since 1793. From the 21st century, a census of communes with fewer than 10,000 inhabitants is held every five years, unlike larger communes that have a sample survey every year.[Note 1]
^At the beginning of the 21st century, the methods of identification have been modified by Law No. 2002-276 of 27 February 2002, the so-called "law of local democracy" and in particular Title V "census operations" allows, after a transitional period running from 2004 to 2008, the annual publication of the legal population of the different French administrative districts. For communes with a population greater than 10,000 inhabitants, a sample survey is conducted annually, the entire territory of these communes is taken into account at the end of the period of five years. The first "legal population" after 1999 under this new law came into force on 1 January 2009 and was based on the census of 2006.