Preterm (PT) infants are at risk of growth failure despite advanced early care and nutrition. In addition to poor weight gain, slow postnatal linear growth also is associated with adverse neurological outcome. Markers distinguishing infants at risk for impaired catch-up growth are needed. The aim of this longitudinal study was to determine the extent to which postnatal levels of circulating cartilage (serum pro-C-type natriuretic peptide [S-proCNP]) and urinary bone metabolic markers (urinary osteocalcin [MidOC] and two forms of C-terminal cross-linked telopeptide of type I collagen [U-α-CTX-I and U-β-CTX-I]) predict catch-up growth in infancy in 67 PT and 58 full-term (FT) infants. PT infants were significantly shorter than FT infants during the first 6 months of life, but no statistically significant difference was found at the corrected age of 14 months (M14). At the age of 3 months (M3), S-ProCNP and U-MidOC levels, but not U-α-CTX-I and U-β-CTX-I levels, correlated positively with prospective growth velocity from M3 to M14 (ρ = 0.460, p <0.001 and ρ = 0.710, p <0.001, respectively). In predicting slow linear growth (growth velocity at the lowest quartile), the area under the S-ProCNP ROC curve was 0.662 and that of U-MidOC 0.891. Thus, U-MidOC, and to lesser extent S-ProCNP at M3 are predictors of catch-up growth in infancy.