Biomarkers are essential part of daily medical practice. Currently, biomarkers are being used both for diagnostic and prognostic purposes. There are many approaches e.g. ELISA by which biomarker levels are detected from patient samples. However, all these approaches are laborious, time consuming and expensive. There is therefore a general need for exploring new technique which can overcome these drawbacks. Here, we present a preliminary study for detection of serum biomarkers by fluorescence correlation spectroscopy (FCS) based diagnostic technique. FCS is a technique basically used for spatial and temporal analysis of molecular interactions of extremely low-concentration biomolecules in solution. FCS is able to measure diffusion time of the fluorescent molecules passing through the open detection volume and it can also measure the average number of fluorescent molecules passing through the detection volume. Because diffusion speed is correlated with shape and molecular mass of the fluorescent molecule, this property makes it possible to study the complex formation between a small fluorescently labelled and a large unlabelled molecule. In this preliminary study, we utilize this FCS property for detection of serum biomarker. Further studies on various pathological serum samples are warranted to explore further aspects of this technique.