Adenosine nucleoside is an important molecule in human physiology. The levels of adenosine nucleoside in urine and plasma are directly or indirectly related to diseases such as neurodegenerative diseases and cancer. In the present study, adenosine-imprinted and non-imprinted poly(2-hydroxyethyl methacrylate-methacrylic acid) (poly(HEMA-MAA)) surface plasmon resonance (SPR) nanosensors were prepared for the determination of adenosine nucleoside. First, MAA/adenosine pre-polymerization complexes were prepared at different molar ratios using adenosine as a template molecule and methacrylic acid (MAA) as a monomer, and SPR nanosensor surfaces were optimized by determining the highest imprinting factor of the chip surfaces. The surfaces of adenosine-imprinted and non-imprinted SPR nanosensors were characterized by using atomic force microscopy, ellipsometry, and contact angle measurements. Kinetic analyses were made with different concentrations in the range of 0.5-400.0 nM for the detection range with a pH 7.4 phosphate buffer solution. The limit of detection in adenosine aqueous solutions, artificial plasma, and artificial urine was determined to be 0.018, 0.015, and 0.013 nM, respectively. In the selectivity analysis of the developed nanosensors, the selectivity of adenosine SPR nanosensors in solutions at different concentrations was determined by using guanosine and cytidine nucleosides. The relative selectivity coefficients of adenosine-imprinted SPR nanosensors for adenosine/cytidine and adenosine/guanosine are 3.836 and 3.427, respectively. Since adenosine-imprinted SPR nanosensors are intended to be used in medical analysis and research, adenosine analysis has also been studied in artificial urine and artificial plasma samples.