Multiple myeloma (MM) patients with chromosome 1q gain (1q+) are clinically and biologically heterogeneous. The underlying molecular mechanisms are still under investigation, while the identification of targets for effective therapy of this subgroup of MM patients is urgently needed. We aimed to investigate the clinical significance and the regulatory mechanisms of insulin-like growth factor 2 messenger RNA (mRNA) binding protein 1 (IGF2BP1), a N6-methyladenosine (mA) reader, in MM patients with 1q+. We found that MM patients with 1q+ exhibit a significantly higher level of IGF2BP1 mRNA than controls, while higher IGF2BP1 expression predicted a worse prognosis in MM patients with 1q+. IGF2BP1 overexpression promoted cell proliferation and G1-to-S phase transition of the cell cycle in NCI-H929 cells. Through comprehensive analyses of existing public datasets and in-house generated high-throughput sequencing datasets, along with experiments, we identified CDC5L as a target of IGFBP1, which can bind to the mA sites of CDC5L mRNA to up-regulate its protein abundance. Higher CDC5L expression also predicted a worse prognosis of MM patients with 1q+. Moreover, both knockdown and mutation of CDC5L attenuated the pro-proliferative effect of IGF2BP1. Furthermore, IGF2BP1 inhibitor BTYNB effectively inhibited CDC5L expression in MM cells with 1q+ and suppressed the proliferation of these cells and . Therefore, IGF2BP1 acts as a post-transcriptional enhancer of CDC5L in an mA-dependent manner to promote the proliferation of MM cells with 1q+. Our work identified a novel IGF2BP1-CDC5L axis and provided new insight into developing targeted therapeutics for MM patients with 1q+.