We have successfully developed a portable electrochemical biosensor that integrates an NFC potentiostat with a sequential flow-through microfluidic device and exploits nanobodies for the capture and quantification of CRP, providing a reliable and inexpensive diagnostic solution. Our device offers user-friendly operation, delivering the test results within 15 min at a cost of under 0.2 € per device. It has a wide linear range of detection (10 ng mL -1 to 100 μg mL -1 ), an elevated LOD of 7.6 pg mL -1 , and demonstrated high specificity for CRP, even in the presence of other proteins commonly found in serum samples. Its reliability was confirmed by the precise detection of CRP in artificial serum, plasma, and whole blood samples, eliminating the need for sample pretreatment steps. Importantly, this configuration can be potentially applied to any soluble biomarkers by simply exchanging the recognition element used to capture the antigens. Thus, it offers an alternative and economically accessible method for the detection of any biomarker, particularly in settings where advanced clinical equipment is lacking.