We used targeted and untargeted profiling approaches to determine differences in plasma biomarkers between the most and the least feed-efficient animals based on residual feed intake (RFI). One-hundred forty-nine Red Angus cattle were allocated to 3 groups according to herd origin. Animals were fed a finishing diet for 78 d to determine the RFI category for each. Within each contemporary group, the 2 most-efficient (n = 6; RFI coefficient = −2.69 +/−0.58 kg dry matter/d) and least-efficient animals (n = 6; RFI coefficient = 3.08 +/− 0.55 kg dry matter/d) were selected. Plasma samples were collected at d 78 for analyses using ELISA and a high-resolution mass spectrometry-based untargeted metabolomics. Metabolites were analyzed using Q-Exactive MS system after LC separation. Data analysis was performed using the MetaboAnalyst 4.0 program. Metabolites with ‘importance in projection (VIP)’ scores >1.0 and a 2-fold difference between groups were considered significantly different. The top 15 metabolites with highest VIP score were identified by molecular weight (mass error ppm <5) for comparison between groups. Biomarker analysis via ELISA revealed that the most-efficient animals had greater activity of paraoxonase (166 vs. 131 U/mL) and lower concentrations of IL-6 (138 vs. 340 pg/mL) and IL1-β (3.7 vs. 17.3 pg/mL) indicating a more pronounced inflammatory status in least-efficient animals. The untargeted metabolomics approach identified 115 distinct metabolite features between groups. Multivariate analysis (PLS-DA and OPLS-DA) demonstrated a clear discrimination between groups. Among the top 15 metabolites identified by the VIP analysis, tumonoic Acid I (VIP = 3.9) was greater in the most-efficient compared with the least-efficient animals. The molecular mass for the remaining 14 metabolites overlapped with more than one molecule in currently available databases, hence, could not be identified with certainty. Overall, the data indicate that targeted and untargeted plasma biomarker profiling could be helpful for identifying RFI-specific systemic compounds that may play a role in determining feed efficiency in cattle.