Objectives: Mother's own milk (MM) is the best nutrition for newborn preterm infants, but is often limited in supply just after birth. Pasteurized human donor milk (DM), and especially preterm infant formula (IF) are less optimal diets than MM. We hypothesized that it is feasible to use bovine colostrum (BC), the first milk from cows, as a supplement to MM, during the first weeks after preterm birth. Methods: In an open-label, randomized, controlled pilot safety trial, supplementation of MM with BC was compared with DM supplementation (Danish unit) or IF supplementation (Chinese unit). If MM was limited or lacking, BC, DM or IF were given according to local feeding guidelines during the first 14 days of life. Results: Forty infants were included and randomized in Denmark and in China, with gestational ages 29.9 ± 0.4 and 31.1 ± 0.2 weeks, respectively. Infants supplemented with BC received more enteral protein (P < 0.05) and tended to reach full enteral feeding earlier (China only). Eight infants fed BC showed a temporary elevation in plasma tyrosine on day 7, versus 2 infants in the DM/IF groups. There were no differences between diet groups in feeding intolerance or clinical adverse events. Conclusions: Our results indicate that it is feasible to use BC as a supplement to MM during the first weeks of life to increase enteral protein intake in preterm infants. Plasma tyrosine levels may be a good marker for excessive protein intake. A larger randomized trial is required to test the safety and possible short- and long-term clinical benefits of BC supplementation during the first weeks of life for preterm infants.