The study evaluated species diversity, including regeneration and growth dynamics of different naturally regenerated tree species in gaps of different sizes in a tropical moist semi-deciduous forest, Ghana. Twenty-three randomly selected gaps categorized as small (≤300 m²), medium (301–1000 m²), large (1001–2000 m²) and very large (>2000 m²) sizes were defined. Forty-one subsampling circular 1 m² plots at 2 m intervals were delineated within each gap. In total, 1468 individuals belonging to 85 species from 25 families and 65 genera were enumerated. Malvaceae (13 species) was the most diverse family, while Bignoniaceae, Clusiaceae, Lecythidaceae, Melastomataceae, Mimosaceae, Myristicaceae, Ochnaceae, Rutaceae, Santalaceae, and Urticaceae families were scarcely represented by only 1 species, respectively. Non-pioneer light demanding (NPLD) recorded the highest number of 38 species, followed by pioneers with 30 species, whereas shade-tolerant attained the lowest representatives of 17 species in regenerated species composition. All estimated diversity indices revealed improvements of species diversity in all gaps significantly. Though the small gaps showed no regeneration shift between pioneers and shade-tolerant, the other gap sizes did it at 62–82%. Medium and large gaps promoted natural regeneration at all distinguished diameter classes, however, pioneers and NPLD at 71–100 mm and pioneers at 51–70 mm were absent in small and very large gaps, respectively. Similarly, pioneers of height 0–20 cm in very large gaps were missing. Conclusively, species biodiversity differed significantly among gaps while regeneration dynamics differed significantly among gap sizes.