The need for high quality evidence is recognized for optimizing practices of parenteral nutrition (PN). The purpose of the present systematic review is to update the available evidence and investigate the effect of standardized PN (SPN) vs. individualized PN (IPN) on protein intake, immediate morbidities, growth, and long-term outcome in preterm infants. A literature search was performed on articles published in the period from 1/2015 to 11/2022 in PubMed and Cochrane database for trials on parenteral nutrition in preterm infants. Three new studies were identified. All new identified trials were nonrandomized observational trials using historical controls. SPN may increase weight and occipital frontal circumference gain and lower the value of maximum weight loss. More recent trials suggest that SPN may easily increase early protein intake. SPN may reduce the sepsis incidence, but overall, no significant effect was found. There was no significant effect of standardization of PN on mortality or stage ≥2 necrotizing enterocolite (NEC) incidence. In conclusion SPN may improve growth through higher nutrient (especially protein) intake and has no effect on sepsis, NEC, mortality, or days of PN.