Arrhythmias are electrical disturbances resulting in irregular heartbeats. Multiple ion channels orchestrate the coordinated propagation of electric stimuli within the heart. Dysfunction of the ion channels, which may result from genetic alterations in ion channel genes or their aberrant expression, can render electrical disturbances predisposing to cardiac arrhythmias. MicroRNA (miRNA) is a type of small RNA belonging to non-protein coding RNAs and is involved in RNA interference, thereby functioning as a regulator of gene expression. Recently, the role of miRNA in cardiac conduction diseases, arrhythmogenesis and their therapeutic potential has been implicated. Stem cell therapies for cardiac arrhythmia have attempted to modulate defective ionic currents by delivering engineered cells. The modulation or engineering of stem cells with appropriate miRNAs could improvise stem cell-based therapies for arrhythmia. This chapter would review the role of miRNAs in cardiac rhythmic disorders and its potential in diagnosis and treatment of cardiac arrhythmia.