The main limitations of uniform half-width microstrip leaky-wave antennas (HW-MLWAs), namely a single operating band and only forward beam scanning, are overcome here with an HW-MLWA loaded with periodic L-shaped slots. The antenna exhibits tri-band operation, and the main beam can be steered in the forward direction in one band, and in the backward direction in the other two bands. Its size is halved with a shorting wall. The antenna was fabricated and tested to validate the concept, and the measured and simulated results agree very well. The measured matched (10-dB return loss) bandwidths of the prototype are 22.34% (5.05-6.32 GHz), 15.85% (8.77-10.28 GHz), and 11.21% (12.63-14.13 GHz) in the first, second, and third bands, respectively. The beam-scanning ranges of the prototyped antenna are 30° to 64°, -75° to -18°, and -19° to -4° when the frequency sweeps from 5 to 6 GHz, 8.85 to 10.5 GHz, and 13 to 14.25 GHz, respectively. The measured peak gains (within the scanning range) are 12.4, 14.3, and 14.7 dBi in the first, second, and third bands with variations of 2.5, 3.4, and 3.1 dB, respectively.