Pesticide application conducted to offer the needed protection to rice plants against weed, disease, insect, and pest infestations. The aim of this study is to investigate the field performance, field time distribution, energy expenditure, mechanization Index, and greenhouse gas emissions from chemicals spraying operation. This conducted study revealed that the wetland paddy fields under transplanting method show 16.3% higher mean effective field capacity, 0.7% lower mean field efficiency, 4.1% lower mean fuel consumption, and 9.5% higher mean operation speed than the fields under broadcast seeding method. The time-motion analysis showed that the laborers spent only 69% of their total working time in the actual spraying task on the crops while the balance 31% of the total operation time was used in filling and mixing pesticides and water in the sprayer tank. The highest contributor to energy expenditure was pesticide energy where it represented 83% to 84.5% of the total energy followed by fuel energy with 14.8% to 13.4%. The total human energy obtained through the conventional method was 34.7% higher mean than the physical human energy recorded using the Garmin method. The heart rate of the worker in performing the spraying operation was the highest compared to the heart rate of the worker in performing the other operations. The total GHG emissions were 66.3 to 92.4 kg CO2eq/ha and chemicals pesticides represent the highest contributor it represented 78.9% to 82.7% of the total GHG emissions. The average mechanization index of the operations in wetland rice cultivation in Malaysia was 70.4%. Fertilizing, planting (broadcasting), and chemicals spraying operation have the lowest mechanization index in wetland rice cultivation.