Abstract:The trade-off seed size/number is a recognized phenomenon capable of shaping ecological processes of colonization and establishment of plant species. Studies that describe trade-offs size/number of seeds in supra-annual fruiting species are still rare. In this study, two predictions for trade-off size/number hypothesis were tested: (i) on a population scale, seeds produced during years of greater reproductive investment showed reduced size, and (ii) on individual scale there is an inverse relationship between size and number of seeds produced by individual plant. To test these predictions, 102 Copaifera langsdorffii adult plants were monitored monthly from January to September during four consecutive years (2008 to 2011) in order to study the reproductive investment of plants. C. langsdorffii plants exhibited reproductive activity only during years 2008 and 2011. The mean number of seeds per branch was 26.4 % greater in 2008 comparatively to 2011. It was also observed that seed size was greater in the year of 2008, when plants produced greater number of fruits. Thus, the data did not support the first prediction of seed size/number hypothesis. In both reproductive years, there was a negative relationship between seed size and number of seeds, supporting the second prediction of the seed size/number hypothesis. The interaction term with the reproductive year suggests that the trade-off size/number of seeds was indeed stronger in 2011, when the plants produced lower seed number. Finally, this study calls the attention to supra-annual fruiting pattern in C. langsdoffii, and suggests that the phenological patterns contribute to explain the wide variation in their seed size and geographical distribution.