Weeds are a perennial problem in coconut plantations and cause significant losses in terms of nut yield. The occurrence of a wide range of weeds also causes difficulties in their eradication. The influence of buffalo grazing on weed biomass and nut yield was evaluated to determine the economical and effectiveness of this method to control weeds in coconut plantations in the low country wet zone of Sri Lanka. Treatments imposed were: tractor slashing as control (T1), cover cropping with Pueraria phaseoloides (T2) and buffalo grazing (T3). Slashing treatment was applied three times per year and buffalo grazing was practiced once a month to control grasses and weeds. The treatments were arranged in a Randomized Complete Block Design with three replicates. Based on the reduction of the weed biomass, treatments T2 and T3 were found to be significantly effective (P<0.05) over slashing treatment. Coconut yield was increased significantly (P<0.05) in buffalo grazing plots and decreased in cover cropping plots. Control of weeds with buffalo grazing and cover cropping with Pueraria resulted in 7% increase and 6% decrease in nut yield over the slashing plots respectively. Buffalo grazing was found to be the most effective method of controlling weeds in coconut plantations. Cover cropping with Pueraria phaseoloides was effective in controlling weeds in the long term, but was not economically beneficial compared with the buffalo grazing. Establishment of cover crop was helpful to conserve soil moisture but it appeared to compete with palms for soil nutrients. A high soil penetrometer resistance in the grazing plots pointed to a significant change in the soil structure as a result of buffalo traffic in the area. Harrowing the buffalo grazing plots appeared to be the best method to overcome soil compaction and finally increase soil aeration and create more favorable environment for palm growth.