Polyurethanes (PUs) were synthesized with polyols derived from castor oil and isophorone diisocyanate. The materials were evaluated for their mechanical properties using stress–strain curves, thermogravimetric analysis, differential scanning calorimetry, and contact angle analysis. The biological response of the materials was evaluated by determining their cell viability in vitro, antimicrobial activity against Escherichia coli and Pseudomonas aeruginosa, and biological response in vivo of PUs by means of implanting them in Wistar rats. The cell proliferation on the materials was analyzed using mouse fibroblast L929, human fibroblast MRC-5, and adult human dermal fibroblast (HDFa) cells by the ISO 10993-5 method. The materials showed no toxic effects and promoted cell proliferation. Experiments performed in vivo for 30 days in mice showed that the materials neither affected the wound healing process nor caused adverse effects or severe injuries in the dorsal mid-cervical tissue or organs on histological evaluation. PUs synthesized can be used in biomedical devices.