Alternative splicing of the CaV α1 subunit adds to the functional diversity of Ca²⁺ channels. A variant with a 73nt deletion in exon 15 of Cav1.2 α₁ (Cav1.273) produced by alternative splicing that predicts a truncated protein has been described but its function if any is unknown. We sought to determine if by analogy to other truncated CaV α₁ subunits, Cav1.273 acts as an inhibitor of wild type Cav1.2 currents. HEK293 cells were transfected with Cav1.273 in either a pIRES vector with CD8 or in pcDNA3.1 with a V5/his C-terminal tag plus β2 and α21 accessory subunits, and pEGFP. Production of Cav1.273 protein was confirmed by Western blot and immunofluorescence. Voltage clamp studies revealed the absence of functional channels in transfected cells. In contrast, cells transfected with full length Cav1.2 plus accessory subunits and pEGFP exhibited robust Ca²⁺ currents. A7r5 cells exhibit endogenous Cav1.2-based currents that were greatly reduced (>80%) without a change in voltage dependent activation when transfected with Cav1.273-IRES-CD8 compared to empty vector or to pIRES-CD8 controls. Transfection of A7r5 cells with an analogous Cav2.373-IRES-CD8 had no effect on Ca²⁺ currents. Immunofluorescence showed intracellular but not plasma membrane localization of Cav1.273-V5/his as well as colocalization with an endoplasmic reticulum marker, ER Lights. Expression of Cav1.273 α₁ subunits in A7r5 cells inhibits endogenous Cav1.2 currents. The fact that this variant arises naturally by alternative splicing raises the possibility that it may represent a physiological mechanism to modulate Cav1.2 functional activity.