Abstract: Groundwater is the principal source of domestic and agricultural water supply in the Nineveh Plain, northern Iraq, where population growth, agricultural expansion, climate variability, and declining surface-water availability have increased pressure on groundwater resources. A study of the groundwater hydrochemistry, irrigation suitability, trace metal occurrence, and microbiological quality was conducted in the Al-Qosh and Tel-Kif area of the Nineveh Plain during summer 2025. The results show that groundwater is predominantly neutral to slightly alkaline and ranges from fresh to moderately mineralized. Based on the FAO/USSL EC-SAR classification for assessing irrigation suitability, most of the samples fall within the C2–S1 and C3–S1 categories, indicating moderate to high salinity with low sodium hazard; thus, they are considered suitable for irrigation of most plants except sensitive one with best management practices. Trace metal concentrations show much compliance with drinking-water standards; however, localized exceedance of arsenic, lead, and uranium presents health risks in select wells. Microbiologically, 28% of the samples were positive for total coliforms or Escherichia coli, rendering the waters unsuitable for direct consumption unless treated. The Nineveh Plain is profoundly dependent on groundwater; however, chemical and microbiological pollution are localized processes that urgently require monitoring, protection, and management measures to secure groundwater sustainability.