This study aims to conduct a life-cycle assessment (LCA) on the efficiency of biohydrogen production from palm oil mill effluent (POME) in laboratory-scale up-flow anaerobic sludge fixed-film (UASFF) and continuous stirred-tank reactor (CSTR). LCA is a tool used to determine the environmental performances of products, processes, or services, through their production, distribution, usage, maintenance, and disposal stage. It is a systematic set of procedures developed to compile, examine, and evaluate the material and energy balance of the system by converting those inputs and outputs to associate with the potential environmental impact that is directly attributable to the operation of a product or service system throughout its entire life cycle. SimaPro software (version 9) was chosen to carry out the LCA of biohydrogen production under the ISO 14040 Standard. The life cycle inventory (LCI) data from Ecoinvent database (version 3.6) libraries were used. The study covered the analysis of the cradle-to-gate system boundary, which contains the raw material and energy acquisition. The assessment was done based on the functional unit of 1 kg biohydrogen production. The POME input to the system is considered a waste product that carries zero environmental loads. The potential of the avoided burden of POME utilization was also not considered in the system boundary. The system boundaries of the biohydrogen production include the inputs: POME, electricity usage (pumps, water bath and stirrer), molasses as fermentation stimulant, and output: emission of biogas (H2, and CO2), and effluent described within the boundary. The density and specific heat of POME used for the analysis are 1007.7 kg/m3 and 4374.89 j/kg. The density of molasses, hydrogen and carbon dioxide gases are 1124.6 kg/m3, 0.08988 kg/m3 and 1.87 kg/m3. The energy conversion factors of 1kWh equal to 3.6 MJ. The inventory analysis was conducted by collecting and calculating the input-output data, which consist of energy flows and material used as defined in the system boundary. The inventory data were collected for the CSTR reactor and the UASFF reactor with both on 24h HRT. The amount of energy usage for both reactors are collected using power meters installed. For CSTR, the electricity consumption for water bath, stirrer and pumps were measured, while, for UASFF, the electricity usage was measured for water bath and pump. The water bath and pump(s) in the UASFF reactor consumed higher amounts of energy compared to the CSTR reactor due to the operating volume of POME in UASFF on average (1.9L) being higher than CSTR (4.2L). The impact assessment results show that in the 24h HRT system, CSTR performed slightly (7%) better than UASFF in terms of carbon footprint (kg CO2e) and energy consumption (MJ) per kilograms of biohydrogen produced. It is also noticed that the water bath was the main contributor to carbon footprint and energy consumption in both reactors with CSTR at an average of 61% and UASFF at 66%. While the pump and stirrer (CSTR only) come second and third. The usage of molasses produced a negative values of carbon footprint due to its carbon sequestration capabilities during its life cycle. The biohydrogen production from CSTR reactor showed a better performance than UASFF reactor in term of carbon footprint and energy consumption.