Abstract: Background and Objective: The plywood processing industry in Indonesia still uses synthetic adhesives which require high temperatures for the adhesive curing process. This study examined the effect of Rhizophora bark tannin on the reduction of adhesive curing temperature of Phenol-formaldehyde during the production of plywood. Materials and Methods: The dried bark was ground and sieved with a mesh size of 20-40. Tannin was extracted from the powdered bark by hot-water extraction at 70°C for 3 hrs with a water-to-bark ratio of 6:1 (w/w basis). The extracted tannin was filtered by using number 1 filter paper and mixed with Phenol-Formaldehyde (PF) resin at various ratios for the production of plywood. Delamination tests, bonding tests, adhesive curing analysis and Scanning Electron Microscopy (SEM) was used to observe the effects of Rhizophora bark tannin on the adhesive curing temperature during plywood production. Results: It was found that the rate of resin reaction increases when tannins are added to the PF resin which causes rapid drying. The addition of tannins to the PF resin reduced the delamination value and met the JAS test standards but it became negative if the amount of tannin added was higher (20%). The bond value in the wet cycle is quite good and has a relatively small reduction (23%). Conclusion: The addition of Rhizophora bark tannins to PF resin reduced the curing temperature of PF resin from 120-105°C. The addition of tannins up to 10% can be used to reduce temperatures up to 15°C in plywood production.