Knowing carbon (C) content variations in forests, provides information relevant to assessing climate change. Traditionally, methods for calculating C content are destructive and do not consider variation in wood density (ρ). In this study, temporal variation in C content of Pinus cooperi Blanco was determined at a site in the Sierra Madre Occidental, Durango, Mexico. Chronologies of carbon capture in this species were obtained using dendrochronology to date growth rings and allometric relationships to estimate biomass, including ρ. Our results indicate that temporal variation in C is related to temporal variation in ρ. Such variation likely depends on environmental and spatial conditions at site. Comparison of our results with those obtained without taking into account ρ shows that neglecting ρ underestimates C capture by more than 50%, representing a variation of up to 266.51 mg at this site. Our more accurate C estimates are relevant to establishing effects of climate change on C flows in ecosystems. This is the first study to use such methodology to estimate C capture in Mexico, providing important information on C flows and forest productivity for this region.