Barley virus G (BVG), the species Polerovirus BVG, within the genus Polerovirus in the family Solemoviridae, represents a new threat to cereal crops in Poland. It was first identified in 2022–2023 using high-throughput sequencing in pooled barley samples exhibiting leaf yellowing and stunting symptoms. The presence of BVG was subsequently confirmed by RT-PCR using diagnostic primers described in the literature. A nucleotide BLAST search of the NCBI database revealed sequence identity ranged from 97.8% to 100%. The final results demonstrated mixed infections involving BVG and luteovirus pashordei, formerly barley yellow dwarf virus—PAS (BYDV-PAS). In 2023–2024, BVG was detected in four additional locations across western, southern, south-eastern, and eastern Poland. The virus was found in co-infection with BYDV-PAS in barley and oat, and with mastrevirus hordei, formerly wheat dwarf virus (WDV) in wheat. Due to the mixed nature of BVG infections, a set of total RNA samples previously isolated from BYDV-infected plants was reanalyzed. RT-PCR results confirmed BVG/BYDV-PAS co-infections in samples collected in 2014–2015, 2018–2019, and 2020–2021. These findings indicate that BVG has been present in Poland for at least 10 years. Molecular characteristics were assessed based on the coat protein gene sequence.