Citrus Huanglongbing (HLB) is the most devastating disease affecting citrus trees, primarily transmitted by the citrus psyllid. Once infected, citrus trees develop mottled yellowing symptoms, and the disease can only be managed by removing and destroying infected trees. This has caused severe economic losses to the global citrus industry. HLB is caused by the phloem-limited bacteria Candidatus Liberibacter asiaticus (CLas). However, the pathogenic mechanism of this disease currently remains unclear. Heavy metal-associated isoprenylated plant proteins (HIPPs) are known to be susceptible genes in plant–pathogen interaction systems and play a crucial role in maintaining heavy metal homeostasis and in responding to biotic and abiotic stresses. Previous studies have shown that citrus HIPP are potential susceptible targets of CLas, with multiple HIPP genes being activated in response to CLas infection. To investigate the function of the HIPP gene family in plant immunity, we used three PCR primers and real-time quantitative PCR to identify T-DNA insertion mutants of the Arabidopsis thaliana HIPP genes. Reactive oxygen species (ROS) and callose deposition triggered by flg22 in T-DNA mutants were analyzed by DAB staining and aniline blue staining. The PCR results showed that six pure mutants with T-DNA insertion were identified, with a downregulated expression level of HIPP genes. Furthermore, the DAB staining results indicated that the ROS triggered by flg22 were not influenced in HIPP gene T-DNA mutants. The aniline blue staining results showed that callose deposition was significantly increased in the HMP1T1, HMP52T, and HIPP22T mutants, while callose deposition was significantly decreased in HIPP3T. These findings suggest that HMP1, HMP52, and HIPP22 of Arabidopsis thaliana may act as negative regulators of plant immunity, whereas the HIPP3 gene may function as a positive regulator. This study provides an experimental basis for further functional analysis of HIPP genes in citrus–CLas interactions and plant immunity.