In this letter, we demonstrate the performance achievable with a highly reconfigurable leaky-wave antenna (RLWA) when used as a building block of a wideband multiple-input-multiple-output (MIMO) communication system. The antenna design consists of a periodic structure, composed of cascaded composite right/left-hand (CRLH) microstrip unit cells with tunable electrical characteristics, that is capable of steering its radiation beam over a wide angular range. Field measurements collected in an indoor environment employing an array of dipoles at the transmitter and the RLWA and an array of dipoles at the receiver are used to measure the RLWA achievable gains. We show that the proposed antenna is capable of providing significant gains, with respect to a traditional array of dipoles, while reducing the space occupied by the antenna on the communication device.