In this study, ornamental cranberry (Cornus Alba) reinforced hybrid composite is synthesized. The plant leaves have been collected, dried, and ground for composite production. After it is reinforced into unsaturated polyester (UP) at different rates by mass, it is mixed to show a homogeneous distribution. Then, 5 wt.% of the total mixture is added to the epoxy resin and polymerization reactions are started with the help of necessary additives and catalysts. The product obtained is poured into standard molds and after waiting one day for curing, necessary tests are carried out. According to the results obtained, biomass supplementation reduces the density of the hybrid composite. Although the addition of epoxy resin increases the hardness of the composite, the ornamental cranberry supplement reduces Shore D hardness. It is observed that the thermal conductivity coefficient decreases as the ratio of polyester resin in the composite increases. However, both epoxy resin and biomass reinforcement slightly raises the thermal conductivity coefficient. Also, high biomass reinforcement both weakens the mechanical strength of the hybrid composite and negatively affects the surface morphology. In this study, it was determined that the composite obtained by using 88.5 wt.% UP, 3 wt.% Epoxy A, 1.5 wt.% Epoxy B, 5 wt.% biomass, 1.5 wt.% methyl ethyl ketone peroxide (MEKP), and 0.5 wt.% cobalt octoate (Co Oc) showed optimum properties.