Fermented goat milk products are considered as specialties in the United States. A probiotic goat milk kefir using polymerized whey protein (PWP) as co-thickening agent was developed. The goat milk kefir (GK) with PWP and pectin had desirable syneresis (5.44 ± 0.92%), viscosity (952.86 ± 61.52 mPa·s) and hardness (112.57 ± 3.23 g), which were comparable to cow milk kefir (CK). Sensory evaluation data (5-point hedonic scale) showed that GK with PWP had a higher scores of both flavor (4.41 ± 0.39) and taste (3.72 ± 0.34) than the sample without PWP. The new product contains 13.02 ± 0.02% total solids, 3.50 ± 0.12% protein, 2.90 ± 0.09% fat, 5.97 ± 0.24% carbohydrates, 0.75 ± 0.02% ash, 0.33 ± 0.02 mg 100 g⁻¹ zinc, 11.50 ± 0.54 mg 100 g⁻¹ magnesium, 140.90 ± 12.24 mg 100 g⁻¹ calcium, 42.20 ± 1.23 mg 100 g⁻¹ sodium and 172.40 ± 11.26 mg 100 g⁻¹ potassium. No significant difference in viscosity and hardness was observed between GK and CK during the 8-week study (P > 0.05). L. Acidophilus population in both GK and CK remained above 10⁶ cfu g⁻¹ during the first 4 weeks. Sodium dodecyl sulfate PAGE photographs showed some changes in the protein profile for both GK and CK during storage at 4°C. Scanning electron micrographs displayed a compact and homogeneous protein network of goat milk kefir with PWP and pectin. Polymerized whey protein may be a novel protein-based thickening agent for formulation of goat milk kefir.