Multimode interference devices using a segment of hexagonal core fiber have been studied numerically and verified experimentally. The devices are capable of transforming light propagation from a standard single-mode fiber to an array of localized self-focusing spots on a hexagonal lattice. Depending on the length of the chosen hexagonal core fiber, the self-focusing pattern can either exhibit a 5-layer matrix with 61 spots or 4-layer one with 37 spots. As 1-to-61 power divider, the optical loss of 2.13 dB and imbalance of 1.25 dB are obtained from the registered power on an infrared camera. Numerical studies have shown that the device can be used as a power splitter from a single-mode fiber to a 61-core- or 37-core-hexagonally packed multicore fiber.