The microwave assisted pyrolysis of oil palm fiber (OPF) for production of hydrogen rich gas was experimentally investigated by considering different reaction parameters. Five different OPF sample sizes (i.e., lengths less than 1mm, 1–3mm, 4–6mm, 7–9mm and 10–12mm), microwave power ranging from 400W to 900W, reaction temperatures ranging from 450°C to 700°C and N2 flow rates ranging 200–1200cm3min−1 were tested. The hydrogen and the total gas yield from all process parameters have been reported. The microwave assisted pyrolysis was carried out by using a microwave reactor which has a capacity of providing 2450±25MHz microwave frequency. It has been found that the use of a smaller OPF particle sizes, a higher microwave power, a higher reaction temperature and a higher N2 flow rates significantly yields more H2 rich gas. The char produced at the maximum hydrogen yield process parameter was considered for TGA and SEM analyses and the results shows a potential use for the soil fertilization.