Ferroptosis, a nonapoptotic form of cell death marked by iron-dependent peroxidation of phospholipids, is associated with the occurrence and progression of tumors. Erastin, a selective inhibitor of the cystine/glutamate transporter system Xc⁻, can induce the ferroptosis of cancer cells. Multiple myeloma (MM) has been reported to be insensitive to erastin-induced ferroptosis. However, we found the erastin sensitivity of different MM cells varied widely. Specifically, SLC7A11 abundance determined the sensitivity of MM cells to erastin-induced ferroptosis. MM cells expressing a high SLC7A11 level were more sensitive to erastin-induced ferroptosis than cells expressing a low level of SLC7A11. Moreover, the expression of SLC7A11 gradually increased with the progression of plasma cell dyscrasias. Survival analysis indicated that high levels of SLC7A11 predicted a poor prognosis for MM patients. Knocking down SLC7A11 expression significantly inhibited the proliferation of MM cells and induced ferroptotic cell death. Additionally, we revealed that the long noncoding RNA (lncRNA) SLC7A11-AS1 was a critical regulatory factor of SLC7A11 expression. SLC7A11-AS1 overexpression diminished SLC7A11 levels, leading to the ferroptosis of MM cells. In summary, our data show that heterogeneous SLC7A11 expression affects MM cell sensitivity to ferroptosis, providing a theoretical basis for improving the clinical treatment of MM.