Palyno-maceral and lithological analysis was carried-out on Mamu Formation, northern Anambra Basin, Nigeria. Analyses of the palyno-maceral composition of the exposed shale unit of the Mamu Formation in the northern Anambra Basin at Ojuwo-Olijo revealed that PM-1 and PM-2 were numerous and poorly sorted, as well as medium to small-sized PM-3 and PM-4, accompanied by Structureless Organic Matter (SOM). This scenario suggests predominantly terrestrial deposition conditions, with possible variations towards coastal and lagoonal environments in certain samples. Diverse pollen and spores, with additional occurrences of Botryococcus braunii, fungal spores, diatom frustules, and rare dinoflagellate cysts were dominant in the samples. The microflora characterization reveals land-derived palynomorphs, including Tricolporopollenites sp., Cyathidites sp., Echitriporites trianguliformis, Longapertites sp., Cyathidites minor, Inaperturopollenites sp., Cingulatisporites ornatus, and Monocolpites marginatus. Biostratigraphic analysis, comparing marker species and diagnostic palynoflora associations places the sediment age within the Campanian to Maastrichtian period. Valuable insights into the Late Cretaceous sedimentary environment were provided by this study, with evidence of terrestrial dominance and occasional transitions to brackish water conditions.