Low potassium intake can affect cardiovascular disease (CVD) risk and cardiometabolic risk factors. We hypothesize that potassium chloride (KCl) supplementation can improve cardiovascular risk metabolomic profile. In this secondary analysis of a pilot randomized clinical trial (RCT) of 26 participants with prediabetes randomized to KCl or placebo, we performed targeted mass-spectrometry-based metabolomic profiling on baseline and 12-week (end-of-study) plasma samples. Principal component analysis (PCA) was used to reduce the many correlated metabolites into fewer, independent factors that retain most of the information in the original data. Those taking KCl had significant reductions (corresponding to lower cardiovascular risk) in the branched-chain amino acids (BCAA) factor (P = 0.004) and in valine levels (P = 0.02); and non-significant reductions in short-chain acylcarnitines (SCA) factor (P = 0.11). KCl supplementation may improve circulating BCAA levels, which may reflect improvements in overall cardiometabolic risk profile. Clinicaltrials.gov identifier: NCT02236598; https://clinicaltrials.gov/ct2/show/NCT02236598.