Objective: To compare the growth of preterm infants fed standard protein-fortified human milk with that containing human milk fortifier (HMF) with a higher-than-standard protein content. Methods: Published articles reporting randomized controlled trials and prospective observational intervention studies listed on the PubMed®, Embase®, CINAHL and Cochrane Library databases were searched using the keywords 'fortifier', 'human milk', 'breastfeeding', 'breast milk' and 'human milk fortifier'. The mean difference with 95% confidence intervals was used to compare the effect of HMF with a higher-than-standard protein content on infant growth characteristics. Results: Five studies with 352 infants with birth weight ≤ 1750 g and a gestational age ≤ 34 weeks who were fed human milk were included in this meta-analysis. Infants in the experimental groups given human milk with higher-than-standard protein fortifier achieved significantly greater weight and length at the end of the study, and greater weight gain, length gain, and head circumference gain, compared with control groups fed human milk with the standard HMF. Conclusions: HMF with a higher-than-standard protein content can improve preterm infant growth compared with standard HMF. Keywords: Human milk; fortifier; growth; meta-analysis; preterm infants; protein.