Positive effects of yeast concentrate on immunity and performance of weaned piglets have been reported. However, the effects on innate immunity were not examined. Natural antibodies (NAb) are part of innate immunity and have been related to health and survival in fish, poultry, rodents, and man. Yeast cell walls may also affect innate immunity of weaned piglets. We studied the effect of Nuklospray ProHealth containing a spray dried blend of dairy-based feed ingredients, vegetable fats, and processed yeast cell walls as protein source on NAb levels and performance of weaned piglets. A total of 120 piglets weaned at 28 d of age were assigned 2 treatments comprising a control diet and an experimental diet with the test product. Piglets were housed in groups of 6 during the first 4 weeks after weaning. Blood samples of 20 healthy nonmedicated piglets per treatment were taken at days 0, 14, and 28 after weaning and analyzed for NAb levels binding keyhole limpet hemocyanin by an indirect ELISA procedure. Performance parameters also were determined. Overall, the experimental diet tended to improve feed intake (574 vs. 522 g/d; P <0.1), ADG (449 vs. 412 g/d; P <0.1), and final BW (21.4 vs. 20.3 kg; P = 0.08) compared to the control diet. No differences were found in feed conversion ratio or fecal score. At day 0, no differences in NAb levels were found, but on day 14 after weaning, NAb levels of piglets fed the experimental diet were significantly higher than of piglets fed the control diet (2.05 vs. 1.70; P <0.05). On day 28 after weaning no differences were found. These results indicate that day 14 postweaning levels of NAb as a parameter of innate immunity were improved and indicate a tendency for improvement of postweaning performance of piglets fed diets supplemented with Nuklospray ProHealth.