We give a general overview on the application of electrochemical analysis to biosensing using nanoparticles (NPs). We describe several examples of applications of voltammetric, potentiometric, conductometric, impedimetric and scanning electrochemical microscope-based methods in NP characterization, detection and quantification. We discuss these examples in terms of sensitivity and selectivity, and other parameters of analytical performance. Using bioassay applications, we discuss the advantages of direct (without previous dissolution) vs. indirect (after dissolution or enhancement) detection of NPs using both voltammetric and potentiometric techniques. In the final part of this review, we describe the use of scanning electrochemical microscopy in characterizing and investigating intrinsic properties of metal and semiconductor NPs. This technique offers a promising approach to future bioanalytical applications, especially for single-molecule detection. The reported electrochemical methods show clear advantages for DNA and protein detection when compared to other techniques, even though application to real samples and development of final market-oriented designs are still awaited.