Meiotic chromosome numbers are reported for 12 species in eight genera of Acanthaceae from Madagascar. Chromosome numbers of 11 species are reported for the first time. Counts in Mendoncia (n = 19) and Neuracanthus (n = 20) are the first for these genera. A new chromosome number (n = 30) is reported in Justicia. Systematic implications of the chromosome counts are addressed and basic chromosome numbers for these eight genera of Malagasy Acanthaceae are discussed.