The temporal variation of biomass and carbon was analyzed in a remnant of the Upper Parana Atlantic Forest (UPAF) in Paraguay, with emphasis on forest dynamics and diameter class distribution. The study used data from trees with a DBH ≥ 10 cm measured in a permanent plot of 1 ha located int the Protected Landscape Laguna Yrendy. Between 2010 and 2017, an average annual increase of 8,14 Mg ha⁻¹ yr⁻¹ in biomass and 4,07 MgC ha⁻¹ yr⁻¹ in carbon storage was recorded. Biomass and carbon gains exceeded losses in all diameter classes, except for class IV. The results suggest that carbon sequestration efficiency could be enhanced through sustainable forest management aligned with the conservation objectives of the protected area. Functional species involved in the carbon storage service, such as Peltophorum dubium, Cordia americana, Handroanthus heptaphyllus, Balfourodendron riedelianum, Cabralea canjerana, and Chloroluma gonocarpa, were identified. These findings provide guidance for managing UPAF remnants to maximize carbon storage and support climate change mitigation.