This paper introduces a novel multimode null reconfigurable antenna (NRA) and its attractive application in grating lobe suppression. The proposed NRA generates a pattern null by combining far fields of TMand TMmodes of a rectangular patch antenna. The theoretical predictions of null angles versus feeding locations are presented based on electric field distributions under the patch. The proposed NRA is realized with a switchable feeding network. Simulated and measured results are presented demonstrating that the pattern null can be switched from -64° to 54° at 2.45 GHz. In final, the proposed NRA is utilized as antenna elements of a sparse array with the element spacing of one wavelength. Simulated array patterns strongly verify the grating lobe suppression capacity of the proposed NRA array compared to the conventional patch array.