In 2019, the bark beetle Ips amitinus (native to central Europe) was identified in south-western Siberia at a distance exceeding 2500 km east of its previously known easternmost location in the European part of Russia. In Siberia, its invasive populations are characterised by high abundance and harmfulness. Here, I. amitinus accomplishes primary attacks on standing vital trees of Pinus sibirica with a lethal outcome. This invasion has already resulted in massive dieback in stands of pine over a large geographic territory. By, 2021, the invaded area was estimated to cover at least 31,200 km2. The objectives of this study were to investigate fungi associated with/vectored by I. amitinus in its invasive area in south-western Siberia and wood decay fungi that cause root and butt rots to P. sibirica. This led to the following conclusions: (i) DNA analysis of sixty adult beetles of Ips amitinus collected from P. sibirica in south-west Siberia revealed the presence of 143 fungal taxa; (ii) species richness was significantly higher in beetles collected from dead branches than from (more recently infested) dying branches; (iii) fungal communities were >90% dominated by yeasts, among which the most common were Nakazawaea holstii, Kuraishia molischiana, and N. ambrosiae; (iv) entomopathogenic Beauveria bassiana s.l. was the most common fungus isolated from dead/mycosed beetles of I. amitinus, followed by Lophium arboricola and four Ophiostoma spp.; and (v) Heterobasidion parviporum was the most common decay fungus detected, which was causing heart rot in stems of P. sibirica.