We analyzed the amine/phenol-metabolome of urine samples to identify urinary metabolic biomarkers associated with residual feed intake in beef cattle. A group of 56 crossbred growing beef steers (average BWВ вҖӢ=В вҖӢ261В вҖӢВұВ вҖӢ18.5В вҖӢkg) were adapted to a high-forage total mixed ration in a confinement dry lot equipped with GrowSafe intake nodes for period of 49В вҖӢd to determine their residual feed intake classification (RFI). After RFI determination, weekly urine samples were collected three times from beef steers with negative RFI (most efficient (HFE); RFIВ вҖӢ=В вҖӢ- 1.93В вҖӢkg/d, nВ вҖӢ=В вҖӢ8) and positive RFI (least efficient (LFE); RFIВ вҖӢ=В вҖӢ+ 2.01В вҖӢkg/d, nВ вҖӢ=В вҖӢ8). Urine samples collected were then composited for each steer. Metabolome analysis was conducted using a chemical isotope labeling/liquid chromatographyвҖ“mass spectrometry, specifically for the analysis of metabolites containing amine/phenol-chemical groups, which are metabolites associated with metabolisms of amino acids. A total number of 557 amine/phenol-containing metabolites were detected and identified. Biomarker analysis of the urinary amine/phenol-metabolome identified N-acetyl-l-tyrosine, O-methyl-l-threonine, uridine, and threoninyl-hydroxyproline as candidate biomarkers of RFI (false discovery rate вүӨ0.05; Area Under the Curve вүҘ0.85). In conclusion, the results of our study revealed that alteration in urine amine/phenol-metabolome is associated with selection for low or high RFI in beef steers and urine is a potential source of metabolite biomarkers associated with RFI in beef cattle.