AbstractInformation about wildlife diets is crucial for comprehending how species adapt to varying environments in fragmented habitats and for developing effective conservation strategies. White‐headed langurs (Trachypithecus leucocephalus) are exclusively found in fragmented limestone forests in southwestern China. To investigate the effects of habitat fragmentation on langurs' diets, we collected published dietary data and relevant environmental factors spanning from 1996 to 2021 at two regions with different degrees of fragmentation (Banli > Bapen), from 10 studies (three of Banli and seven of Bapen). The results demonstrated that the diets of white‐headed langurs were significantly influenced by environmental factors, including habitat fragmentation, annual rainfall, and mean annual temperature. Food item diversity index was significantly and positively affected by the fragmentation index, the higher fragmentation the langurs suffered, the more diverse food items they consumed. Besides, fruit consumption was negatively influenced by annual rainfall and the consumption of other items was influenced by mean annual temperature. Notably, although there are no significant differences in the feeding proportions of food items or food item diversity indices were observed between the Banli and Bapen groups, the Banli groups extensively consumed ground‐supported kudzu (Pueraria montana var. lobata), a plant rarely recorded in the dietary preferences of the Bapen groups, implying that the large plants likely lacking in the fragmented limestone forests. Our findings provide evidence of the major impact of habitat fragmentation on the dietary composition of white‐headed langurs, highlighting the need of considering the possibility that the habitats of the white‐headed langurs have all undergone extreme fragmentation, inferring the conservation efforts should prioritize protecting native vegetation and reducing human disturbance.