In cardiac myocytes the type‐2 inositol 1,4,5‐trisphosphate receptor (IP₃R2) is the predominant isoform expressed. The IP₃R2 channel is localized to the SR and to the nuclear envelope. We studied IP₃‐dependent nuclear Ca²⁺ signals ([Ca²⁺]_Nuc) in permeabilized atrial myocytes and in isolated cardiac nuclei. In permeabilized myocytes IP₃ (20 μm) and the more potent IP₃R agonist adenophostin (5 μm) caused an elevation of [Ca²⁺]_Nuc. An IP₃‐dependent increase of [Ca²⁺]_Nuc was still observed after pretreatment with tetracaine to block Ca²⁺ release from ryanodine receptors (RyRs), and the effect of IP₃ was partially reversed or prevented by the IP₃R blockers heparin and 2‐APB. Isolated nuclei were superfused with an internal solution containing the Ca²⁺ indicator fluo‐4 dextran. Exposure to IP₃ (10 μm) and adenophostin (0.5 μm) increased [Ca²⁺]_Nuc by 25 and 27%, respectively. [Ca²⁺]_Nuc increased to higher levels than [Ca²⁺]_Cyt immediately adjacent to the outer membrane of the nuclear envelope, suggesting that a significant portion of nuclear IP₃ receptors are facing the nucleoplasm. When nuclei were pretreated with heparin or 2‐APB, IP₃ failed to increase [Ca²⁺]_Nuc. Isolated nuclei were also loaded with the membrane‐permeant low‐affinity Ca²⁺ probe fluo‐5N AM which compartmentalized into the nuclear envelope. Exposure to IP₃ and adenophostin resulted in a decrease of the fluo‐5N signal that could be prevented by heparin. Stimulation of IP₃R caused depletion of the nuclear Ca²⁺ stores by approximately 60% relative to the maximum depletion produced by the ionophores ionomycin and A23187. The fluo‐5N fluorescence decrease was particularly pronounced in the nuclear periphery, suggesting that the nuclear envelope may represent the predominant nuclear Ca²⁺ store. The data indicate that IP₃ can elicit Ca²⁺ release from cardiac nuclei resulting in localized nuclear Ca²⁺ signals.