Cassava-based dried distiller’s grain (Cassava-based DDG) is known as a by-product of the bio-ethanol industry with low nutritional value due to the presence of cyanide and to the low content of protein. More value can be added to cassava-based DDG through solid-state fermentation (SSF) using mold and yeast. SSF were conducted with cassava-based DDG in 8 and 5 days of fermentation, respectively. Under optimal conditions, the crude protein fraction of cassava-based DDG fermented by Trichoderma harzianum BiomaTH1 or Yarrowia lipolytica W29 was increased from 11.84% DM for unfermented sample to 15.29 and 14.06% DM, respectively. In addition, the total amino acids of fermented samples using T. harzianum and Y. lipolytica was increased from 11.01% DM to 13.86% DM and 12.39% DM along with an increase in the essential amino acids content which enhanced by 55% and 22%, respectively, including limiting amino acids in pig feeds. The in vitro protein digestibility was improved significantly from 82.5% to 89.2 and 86.9% for T. harzianum and Y. lipolytica fermentation, respectively. Beside increasing the nutritional value, the SSF showed a clear effect in reducing cyanide content of raw cassava DDG from 62.3 mg/kg DM to 24.3 and 53.6 mg/kg. The obtained results indicated that the protein enrichment of this bio-ethanol by-product using mold and yeast fermentation could be very promising to be used efficiently as a cheap and abundant source of essential amino acids for animal feed ingredients in Vietnam. The nutritional projection of adding this cheap ingredient was discussed.