The research aimed to identify and characterize crown gall pathogen that affects apple trees planted in Nineveh and Dohuk governorates. Based on its biochemical, and molecular characteristics, Agrobacterium tumefaciens colonies appeared yellow-green, on D1 Agar, on nutrient agar colonies were creamy white, smooth, convex, round, and regular margins emerged. The colony's color darkens and turns gelatinous with age. A. tumefaciens are Gram-negative and showed positive results forthe generation of catalase, urea, indole, 3-ketolactose, citrate utilization, motility , carbohydrate fermentation, KOH solubility, growth at 35 °C, and growth with 2% NaCl, A. tumefaciens infection was observed. By developing gall on apple seedlings cultivated. In vitro, A. tumefaciens demonstrated its capacity to grow tumors on carrot discs. When infected tobacco leaves, it simultaneously produced a favorable effect, demonstrating the responsiveness of tobacco leaves to it. Furthermore, A. tumefaciens isolates were used to inoculate tomato plants, which is thought to be a crucial diagnostic technique for identifying the source of crown gall disease.