The morphological diversity of pollen brings important information on the taxonomy of plants present in past and current ecosystems. Regarding the rich biodiversity and the large number of endemic plant species on the island of Madagascar, pollen reference collections are still scarce for this part of the world. The main objective of this study was to conduct a preliminary investigation of pollen morphology of flowering plants visited by honeybees in a tropical rainforest of the south-east part of Madagascar during 2014 to 2015 (Ranomafana National Park – Fianarantsoa). Samples of 135 species belonging to 105 genera and 52 families were processed, employing the standard acetolysis method. Pollen reference slides of these melliferous plants were mounted. These pollen grains were then photographed and measured using light microscopy. The 135 collected species include 54 trees, 47 shrubs, 21 herbs, 12 lianas and one epiphyte, among which 85 taxa are endemic, 46 indigenous and four exotic. Pollen morphological characteristics of 106 species (85% endemic) are described here for the first time. Since these endemic plant taxa have co-evolved with the endemic honeybee of Madagascar, Apis mellifera unicolor, the implications of the pollen grain morphology for plant–pollinator co-evolution are discussed.