Aims: The effect of different types of fungal inocula to the cellulase activity measured on palm kernel cake (PKC) was studied. Methodology and Results: Isolate Pro-A1 which was identified as Trichoderma sp. was selected as a potential producer of cellulase via solid state fermentation technique (SSF). Two types of PKCs were used; raw PKC (containing residual oil) and defatted PKC. The PKCs were inoculated with different concentrations of conidia and varying amounts (g) of solid mycelia plugs (SMP) for SSF. The effect of ultrafiltered crude fungal filtrate (CFF) as inocula was also being tested. The highest cellulase activity of 2.454 FPU/mL was detected with 60% (wt/wt) SMP applied to the raw PKC. Conversely, 2.059 FPU/mL of cellulase activity was measured when 80% (wt/wt) of SMP was applied to the defatted PKC which is 62.3% higher than the untreated defatted PKC; and more than 100% increase in enzymatic activity compared to raw PKC. The cellulase activity in the SSF inoculated with 8 x 106 conidia /mL and 12 x 106 conidia /mL were 1.704 FPU/mL for raw PKC and 1.856 FPU/mL for defatted PKC, an enhancement of about 46% from uninoculated batch. Inoculation with CFF bears corresponding maximum improvement of the cellulase activity on both PKCs of 13.58% (raw) and 2.86% (defatted). Conclusion, significance and impact of study: The current study proves that Trichoderma sp. in the form of SMP can enhance the cellulase activity on PKCs effectively with more than 100% increment. Fungal conidia are also a better choice in enhancing cellulase activity of Trichoderma sp. permitted that the PKC used is devoid of oil. From this study, Trichoderma sp. holds the potential of converting lignocellulosic materials into products of commercial and industrial values such as glucose and other biofuels.