Colomerus vitis (Pagenstecher) (Acari: Eriophyidae), commonly known as the erineum leaf mite, is an eriophyid mite that induces characteristic galls and deformities on the leaves and young shoots of Vitis vinifera cultivars. The present study aims to describe the symptomatic manifestations of C. vitis infestation, document its key biological features, and assess its potential ecological impact on vineyard ecosystems in eastern Romania. Observations were conducted during the active vegetative growth period across multiple cultivars and growth stages. Symptoms were systematically recorded through visual inspections and high-resolution photography, revealing leaf galls, curling, and shoot distortions of varying intensity depending on cultivar and plant age. Microscopic examinations confirmed the presence of mites within galls and allowed detailed observation of their morphology, spatial distribution, and population density, offering additional insights into their development and colonization patterns. Differences in symptom severity among cultivars indicated variability in host susceptibility and damage extent. Although C. vitis is not considered an invasive species in Romania, its growing prevalence and the potential for expansion under changing climatic conditions highlight its ecological significance. Recent data on the biology and damage patterns of C. vitis suggest that its increased prevalence, driven by warmer winters, may alter vineyard ecosystem dynamics and potentially increase the risk of transmitting viral pathogens, such as Grapevine Pinot gris virus (GPGV). These shifts emphasize the need for integrated pest monitoring and biodiversity-oriented management strategies. By documenting both macroscopic and microscopic features in a detailed and systematic manner, this study provides comprehensive descriptive information on the biology and symptomatic expression of C. vitis, contributing to a better understanding of arthropod–plant interactions and supporting future research on cultivar susceptibility, ecological resilience, and sustainable viticulture.