Alginate is a key scaffold for cartilage tissue engineering. Here, we systematically evaluated four biomedical and two non-biomedical grade alginates for their capacity to support the in vitro culture and in vivo transplantation of articular chondrocytes. Chondrocytes in all ultrapure alginates maintained a high cell viability. Spheres composed of biomedical grade, low viscosity, high mannuronic acid content alginate showed the lowest decrease in size over time. Biomedical grade, low viscosity, high guluronic acid content alginate allowed for optimal cell proliferation. Biomedical grade, medium viscosity, high mannuronic acid content alginate promoted the highest production of proteoglycans. When transplanted into articular cartilage defects in the knee joint of sheep in vivo, empty spheres were progressively surrounded by a granulation tissue. In marked contrast with these observations, all alginate spheres carrying allogeneic chondrocytes were gradually invaded by a granulation tissue containing multinucleated giant cells, lymphocytes, and fibroblasts, regardless whether they were based on biomedical or non-biomedical grade alginates. After 21 days in vivo, transplanted chondrocytes were either viable or underwent necrosis, while apoptosis played a minor role in their early fate. The individual characteristics of these alginates may be valuable to tailor specific experimental and clinical strategies for cartilage tissue engineering.