Pacemaker therapy for the treatment of bradyarrhythmias and heart failure has continued to evolve over the past decades. The increasing complexity of the devices and the wide disease spectrum that is treated result in situations that may challenge even the most experienced providers. Developing skills to understand device function and device behavior, and to make use of device diagnostic data, is essential to provide optimal care for patients with these devices. This article presents a general approach to device troubleshooting and discusses specific problems that may be encountered in routine clinical practice.