The nutritive values of non-processed and processed pistachio peel with Neurospora sitophila were evaluated. The chemical composition of samples was evaluated by laboratory analysis. An in vitro digestibility study was done to determine digestibility coefficients of dry matter (DM), organic matter (OM). Digestible organic matter in the dry matter (DOMD) to estimate the metabolizable energy (ME) content of pistachio peel samples. In addition, the disappearance of DM, OM and crude protein (CP) of the samples was deter-mined by an in situ method. For each sample 12 bags were incubated for 0, 3, 6, 12, 24, 48 and 72 h and their kinetics were described using the equation p=a+b(1-e-c(t-tl)). The nutritive value index (NIV) of samples was calculated using the equation: NIV=a+0.4b + 200c. The collected data were analyzed in a completely randomized design. The average total phenolic and total tannin compounds, DM percentage and digestion coefficient of DM in pistachio peel decreased (P<0.05) by processing. However, the percentage of CP, acid detergent fiber (ADF), acid detergent lignin (ADL), effective DEGRADABILITY of DM, OM and CP, and NIV of DM, OM and CP increased (P<0.05). The results showed that processing of pistachio peel with Neurospora sitophila, decreased compounds of phenol and tannin and increased its CP and effective DEGRADABILITY.