The paper presents a millimeter-wave wideband dual-polarized low-temperature co-fired ceramics (LTCC) antenna array based on metasurfaces for beam-scanning applications. Benefiting from the wideband and large-freedom property of metasurface-based structures, a novel ±45° dual-polarized wideband metasurface-based antenna (MSA) element with high isolation is designed. The antenna element is fed by two orthogonal striplines on different layers, through a cross-like dog-bone slot and a narrow slot, respectively, to realize the two polarizations. The feeding structure consists of slot–stripline– slot–stripline from top to bottom and is specially designed to improve the polarization isolation of the antenna element. The proposed MSA element is compactly arranged with a small distance (<0.5λ) to construct a 4×4 array integrated in an LTCC package, where via walls with metal ring strips are loaded between adjacent elements to reduce the gain fluctuation. Consequently, the array can achieve a good beam-scanning capability over a wide band of 19.5% with maximum scanning angle up to ± 55° and a small gain variation of less than 3 dB. Meanwhile the active S parameters almost always remain below -10 dB, enabling good impedance matching when scanning at all angles. With these features, the proposed design has potential for application in 5G base-station systems.