A pattern reconfigurable quarter-mode substrate integrated waveguide (QMSIW) antenna with a low profile is proposed in this communication. First, a slot is etched on a QMSIW cavity as a radiating element. Two cavity modes including a quarter mode (QM) and an eighth mode are utilized to obtain the enhanced bandwidth. Then, four quarters sharing the same edge metalized vias are placed in a back-to-back configuration. In this way, the antenna structure is very simple and compact. By choosing the corresponding feed port and phase, nineteen-beam steering including four single-fed tilted beams in total space quadrants (5.8 dBi, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta _{\mathbf {max}} = 20^{\circ }$ </tex-math></inline-formula> ), eight multifed tilted beams in total space quadrants (6.4 dBi, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta _{\mathbf {max}} = 30^{\circ }$ </tex-math></inline-formula> ), four double beams, one semidoughnut beam (3.9 dBi), one toroidal beam (1.1 dBi), and one axial beam (7.7 dBi) can be obtained. The antenna can operate at 2.5 GHz with a height of 1.5 mm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{\mathbf {0}}$ </tex-math></inline-formula> /83).