Palm kernel cake (PKC) is abundantly generated in palm kernel crushing plant throughout the year. Its use as monogastric animal food source is very limited due to its high fibre and moderate protein content. Therefore, this study is aimed to enhance PKC nutritional value, particularly the protein content through solid state fermentation (SSF), using a locally isolated fungus. Fungal identification was performed using partial 18S ribosomal ribonucleic acid (rRNA) nucleotide sequence. A fungus containing 600 base pairs was sequenced and aligned with GenBank database and named Rhizopus oryzae ME01. SSF was carried out using palm kernel expeller (PKE) which is mechanical pressed and palm kernel cake (PKC) which is solvent extracted, as a single carbon source with minimum mineral addition. Results showed that SSF successfully increased crude protein and ash content of fermented PKC and PKE, respectively. Interestingly, this study also found that the size of PKC’s particle had impacted protein content of fermented palm kernel cake (fPKC) during SSF. PKC which has a smaller and uniform size than PKE, gave higher crude protein increment than fermented palm kernel expeller (fPKE). However, the protein content of fPKE had increased by 7.64% more than fPKC which was only 3.45%. Thus, fPKE appeared to enhance PKE’s nutrient value, especially for monogastric animal feed applications.