1. Plant diversity has been found to increase herbivore diversity, including abundance, species richness, and phylogenetic diversity. However, it is yet to be established at which spatial scale these effects are strongest, because host finding and community assembly may be shaped by host diversity both in local habitat patches and at larger scales. 2. Using arthropod herbivore data collected from a large biodiversity and ecosystem function experiment in China (BEF-China), we analyzed how habitat patch (individual study plots) and larger-scale (surrounding study plots) tree diversity relates to species richness, abundance, functional diversity, and phylogenetic diversity of herbivore assemblages on focal plants. 3. Tree diversity of both the focal habitat patch and larger-scale patch neighborhood affected herbivore diversity patterns and host plant selection, with the effect being greater for the former. Furthermore, focal and neighboring trees that are phylogenetically related were found more likely to share similar herbivores. 4. Synthesis. By focusing on tree diversity effects of both the local habitat patch and wider patch neighborhoods, our findings highlight the importance of considering additional scales to give a more nuanced understanding of the mechanisms underlying herbivore community structure and diversity patterns in species-rich forests.