Genetically encoded biosensors that make use of fluorescence resonance energy transfer (FRET) are important tools for the study of compartmentalized cyclic nucleotide signaling in living cells. With the advent of germ line and tissue-specific transgenic technologies, the adult mouse represents a useful tool for the study of cardiovascular pathophysiology. The use of FRET-based genetically encoded biosensors coupled with this animal model represents a powerful combination for the study of cAMP signaling in live primary cardiomyocytes. In this chapter, we describe the steps required during the isolation, viral transduction, and culture of cardiomyocytes from an adult mouse to obtain reliable expression of genetically encoded FRET biosensors for the study of cAMP signaling in living cells.