It has been previously shown that communications in tunnel environments can be improved by using multiple-input-multiple-output (MIMO) techniques, despite the small angular spread of the rays. However, narrowband transmission was always assumed to fulfill the flat channel hypothesis. The objective of this letter is to generalize these previous works to the case of a wideband communication, i.e., when the transmission bandwidth is much larger than the coherence bandwidth of the channel. Performances of MIMO combined with orthogonal frequency division multiplexing (MIMO-OFDM) are studied in terms of bit error rate and considering either space-time coding or spatial multiplexing. Transfer matrices of the channel measured in a straight arched tunnel are introduced in the software used for simulating the communication link.