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 1 mm, 1–3 mm, 4–6 mm, 7–9 mm and 10–12 mm), microwave power ranging from 400 W to 900 W, reaction temperatures ranging from 450 °C to 700 °C and N2 flow rates ranging 200–1200 cm3 min−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 ± 25 MHz 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.