In a survey of fungal species associated with walnut kernel rot symptoms, a white fungal mycelial mass was observed in feces and larval debries of codling moths (Cydia pomonella) on walnut kernels in East and West Azerbaijan provinces in 2022. Infected samples were examined under a stereo microscope, white mycelial mass together with fungal spores were taken using a sterile needle, and pure cultures were established using the single spore method. Morphological characteristics were examined on potato dextrose agar (PDA) and malt extract agar (MEA) culture media in the dark at 21°C after one week of incubation. To confirm the identity of the isolated fungi, the ITS rDNA genomic region of representative isolates were amplified using a universal primer set (ITS1 and ITS4) via polymerase chain reaction, and PCR products were sequenced. Based on the combination of morphological features and sequencing data, the isolates were identified as Quambalaria cyanescens. Colonies grew slowly, reaching a diameter of 11-12 mm on PDA and MEA after one week, and produced a purple pigment in the medium. Conidiophores are undifferentiated from vegetative hyphae and conidiogenous cells are holoblastic with sympodial proliferation. The conidia are usually ovoid or pear-shaped, transparent and 2-8 × 1.5-2.5 µm. Quambalaria cyanescens is a rare basidiomycete species of the order Microstromatales, which also has a yeast phase. The pathogenic potential of the two isolates of Q. cyanescens was evaluated on larvae of Ephestia kuehniella; however, the survival rate of larvae treated with different concentrations of Q. cyanescens spores was the same as that of untreated control larvae, and it can be concluded that the Q. cyanescens isolates were not pathogenic to E. kuehniella larvae. To the best of our knowledge, this is the first report on the association of Q. cyanescens with feces and larval debries of codling moths on walnut kernels.