Mithramycin (MTM) has potent anticancer activity, but severe toxicities restrict its clinical use. Semi‐synthetic approaches have yielded novel MTM analogs with potentially lower toxicity and similar efficacy. In an effort to transition these analogs into in vivo models, a bioanalytical method was developed for their quantification in mouse plasma. Here we present the validation of the method for the quantitation of mithramycin SA‐tryptophan (MTMSA‐Trp) as well as the applicability of the methodology for assaying additional analogs, including MTM, mithramycin SK (MTMSK) and mithramycin SA‐phenylalanine (MTMSA‐Phe) with run times of 6 min. Assay linearity ranged from 5 to 100 ng/mL. Accuracies of calibration standards and quality control samples were within 15% of nominal with precision variability of <20%. MTMSA‐Trp was stable for 30 days at −80°C and for at least three freeze–thaw cycles. Methanol (−80°C) extraction afforded 92% of MTMSA‐Trp from plasma. Calibration curves for MTM and analogs were also linear from ≤5 to 100 ng/mL. This versatile method was used to quantitate MTM analogs in plasma samples collected during preclinical pharmacokinetic studies.