This study aimed to identify some of the main weed species in the pineapple crop grown in northern Minas Gerais state, Brazil. The phytosociological survey was carried out in two seasons, spring-summer and fall-winter, in a pineapple cultivation area of Unimontes, using the square inventory method (0.25 x 0.25 m). The samples were identified and quantified by families, genera and species, evaluating: frequency, relative frequency, density, relative density, abundance, relative abundance, importance value index, relative importance value index and similarity index. In the spring-summer period, ten species were identified, distributed in nine genera and eight families, highlighting the Euphorbiaceae and Poaceae families, with two species each. The species with the highest importance value indexes were Cyperus iria (77.29), Cynodon dactylon (51.99) and Euphorbia heterophylla (45.46). In the fall-winter period, six families, seven genera and nine species were identified, since three of the Euphorbiaceae family, with more species. The species that showed greater importance value indexes in the fall-winter period were Amaranthus hybridus (48.64), Cyperus hiris (48.11) and Euphorbia hirta (45.06). The similarity index was 84.21%, with 11 species in common, demonstrating a high homogeneity between the two evaluated periods.