Although male mating signals often differ between closely related species in nature, existing theory suggests that divergence in male mating signals and female preference is difficult between populations with gene flow. A recent model of ecological speciation under divergent natural selection by van Doorn et al. (2009) showed that if the quality of male sexual ornaments indicated his ecological performance in the local environment, sexual selection and divergent natural selection synergistically increased ecological divergence between populations, leading to speciation. However, this model does not consider divergence in male ornaments and female mate preference, although a general empirical pattern is that divergence in mating characters is common among closely-related species. Here, we construct a model that permits divergence in male ornaments and female preference. The model finds that divergence can occur, although temporal with populations shifting between diverged and un-diverged states. Divergence is likely when the expression of ornaments and the strength of female choosiness have evolved to certain levels, suggesting that increased female sensory accuracy to male ornaments facilitates divergence. We conclude that condition-dependent expression of male sexual ornaments may be important for causing the divergence of male ornaments and female preference in speciation with gene flow.