To make mechanical dewatering of peat economically competitive to conventional peat harvesting, a DS content of about 50% must be achieved after the pressing stage. A pretreatment of the peat involving the addition of chemicals is necessary to reach a high dewatering capacity. In the papermaking industry, systems with two different polymers are used as retention agents. Paper pulp is similar to peat in several aspects. The aim of this study was to investigate the effect of a dual polymer system using two oppositely charged polymers on flocculation and dewatering of peat. In the investigation, an anionic polymer and a cationic polymer, earlier used as single polymer system in peat dewatering, were used in combination. In the peat slurry the dual system gave larger aggregates than the anionic polymer alone and smaller aggregates compared to the cationic polymer alone. From this study it can be concluded that the cationic polymer has a stronger influence on the dewatering properties than the anionic polymer. The anionic polymer was also more dependent of the surface load than the cationic polymer. In low-pressure filtration and during the initial phase of a high-pressure dewatering, an additive effect between the two polymers could be seen. The final DS content after completion of the high-pressure dewatering stage was, however, almost completely dependent on the concentration of cationic polymer.