A new design for a hybrid fiber‐planar refractive index sensor based on the surface plasmon resonance effect is presented. The key element of the design is a thin layer of gold covering a tilted fiber Bragg grating. In the study, a specially developed microfluidic chip is used to perform measurements directly in the flow of the investigated liquid. Rigidly mounting the sensor to the base of the fluid chip is proposed. The presented experimental data demonstrate the high stability of the sensor readings and the low noise level during measurements in a liquid flow. The proposed construction is a promising decision for application in compact immunoassay systems based on microfluidic technologies.