The developed piezoelectric quartz crystal microbalance sensor was compared with the commercial resonant mirror-based optical biosensor IAsys. The former one was based on 10 MHz crystals and flow-through arrangement, the latter employed a stirred cuvette. The same biosensing layers were produced by immobilization of 4,4′-dichlorobiphenyl on aminosilanized surfaces through an albumin bridge. The affinity binding of three corresponding polyclonal antibodies was studied and the kinetic rate constantskaandkdwere determined. The same values of constants were obtained for sheep antibody, smaller values ofka(approx. twice) were obtained for the other two lower-affinity antibodies using the piezosensor. In the additional comparison during a competitive assay of atrazine, both transducers were able to distinguish 0 and 0.1 μg/L atrazine, however, the IAsys signal was less noisy. For bioaffinity kinetic studies, the piezoelectric biosensor was found to be an economic alternative to the advanced optical biosensors.