Background <p>Physical frailty is highly prevalent in heart failure (HF), but we lack an understanding of the underlying pathophysiology. Proteomic evaluation of plasma samples may elucidate potential mechanisms and biomarkers of physical frailty in HF.</p> Objectives <p>We aimed to identify plasma proteomic biomarkers that are differentially expressed between physically frail and non-physically frail adults with HF.</p> Methods <p>This was a secondary analysis of a subset of data and plasma samples from a study of frailty among patients with New York Heart Association (NYHA) Functional Classification I-IV HF. Physical frailty was measured using the Frailty Phenotype Criteria. Propensity score matching was used to match pairs of physically frail (<i>n</i> = 20) vs. non-physically frail (<i>n</i> = 20) patients on clinical characteristics. Plasma samples were processed using a sensitive liquid chromatography mass spectrometry platform, utilizing a multiplexed tandem mass tag-labeled quantitative proteomics approach. Differentially expressed proteins were quantified individually using paired t tests with associated log fold change of 0.3 and Fisher’s combined p values.</p> Results <p>The sample (<i>n</i> = 40) was 62.8 ± 16.9 years old, 58% female, and 55% NYHA Class III/IV. Proteomic analysis revealed 7 proteins differentially expressed using full differential criteria: matrix metalloproteinase-14 was downregulated in frailty, and copine-1, low affinity immunoglobulin gamma Fc region receptor III-A and III-B, probable non-functional immunoglobulin kappa variable 2D-24, glutathione S-transferase Mu 1, and argininosuccinate lyase were upregulated in frailty.</p> Conclusions <p>Proteomic biomarkers related to the immune system, stress response, and detoxification were differentially expressed between physically frail and non-physically frail adults with HF.</p>