Juvenile idiopathic arthritis (JIA) refers to any type of chronic arthritis that develops before the age of sixteen, lasts longer than six weeks, and has an unknown etiology. The existing diagnostic techniques for JIA are conventional and occasionally ineffective at distinguishing JIA from other pediatric illnesses because of their low specificity. This study was a comparative cross-sectional investigation finding prospective future biomarker candidates in JIA patients. A label-free mass spectrometry and bioinformatics tool were used in this study to examine the functional importance of proteins which were differentially expressed in JIA patients compared to their healthy counterparts. Receiver operating characteristic (ROC) curves were used to evaluate the predictive power of screened proteins, and they were validated in a different cohort using ELISA and Western blot analysis. It has been discovered that the JIA group has higher expression of two DEPs (Differentially Expressed Proteins), namely Myosin light chain 12b (Myl12b) and Mannose-binding lectin serine protease1 (MASP1) which showed good predictive abilities in ROC analysis. According to our research, these two proteins upregulated in JIA, Myl12b and MASP1, may serve as biomarkers for the diagnosis and treatment approaches of JIA.The study was a comparative cross-sectional study. The samples were obtained from a tertiary care hospital after obtaining approval from Institutional ethics committee.Samples were screened based on ILAR categorization criteria and the homogeneity of their preliminary biochemical evaluations. EDTA blood samples were collected from diagnosed active poly JIA patients. Plasma was separated, and highly abundant proteins were depleted using immunoaffinity techniques to enrich low-abundance proteins. After immune depletion, the proteins were concentrated, quantitated and normalised to 1mg/ml. The normalised samples underwent mass spectrometric analysis to identify low-abundance plasma proteins.The mass spectrometric analysis revealed several differentially expressed low-abundance plasma proteins in JIA patients. This research could pave the way for improved diagnostic and prognostic tools, as well as potential therapeutic targets for JIA, ultimately contributing to better patient outcomes.