This article reports on a crosslinguistic comparative study of the processing of Japanese relative clauses (RCs) by Chinese-, Sinhalese-, Vietnamese-, Thai-, and Indonesian-speaking second language (L2) learners. A robust finding in studies on the acquisition of RCs in L2 English and other European languages is that subject-gap RCs are easier than object-gap RCs, both in production and comprehension. However, in the case of L2 Japanese studies, the picture does not seem to be as clear as in the English case. This study identifies some factors that might contribute to this situation. The results of a listening comprehension test involving reversible and nonreversible test sentences show that the five groups of learners overall found subject-gap RCs easier to process than object-gap RCs, but that their performances are poor and vary for sentence types in which no semantic cue is available to help identify the grammatical function of the overt noun phrase in RCs, yielding inconclusive results with respect to the question of whether subject-gap RCs are easier than object-gap RCs. Results indicate that when RCs are too difficult for learners to process, first language properties such as head direction, word order, and the relative order of filler and gap affect the manner in which they are interpreted.