DNA interstrand crosslinks (ICLs) are highly toxic DNA lesions that block DNA replication and transcription by preventing strand separation. ICL-inducing agents, such as nitrogen mustards, cisplatin, and mitomycin C, are widely used in chemotherapy. Recent research has revealed how cells repair ICLs, particularly through the Fanconi anaemia (FA) pathway, which involves nucleases, helicases, and other DNA-processing enzymes. Understanding this pathway could lead to more targeted cancer treatments and insights into drug resistance. The use of ICL-inducing agents in chemotherapy originated from the horrors of chemical warfare in WWII. The SS John Harvey, a ship carrying mustard gas, was bombed, leading to the discovery of the drug's potential in treating leukemia. Since then, ICL-inducing agents have become key in cancer treatment, though their role in causing cancer is less clear. ICLs can cause various DNA lesions, and exposure to high levels of natural ICL-inducing agents is rare. ICLs are formed by chemical reactions with bases on opposing DNA strands, leading to covalent bonds that are usually irreversible. Intrastrand crosslinks are less toxic as they can be bypassed by some DNA polymerases. The repair of ICLs involves complex coordination of DNA repair processes, including homologous recombination (HR), nucleotide excision repair (NER), and translesion synthesis (TLS). Defects in these processes can cause cancer but also sensitize cancer cells to ICL-based chemotherapy. FA is a rare genetic disorder linked to ICL sensitivity, characterized by bone marrow failure and increased cancer risk. The FA pathway involves the FA core complex, which monoubiquitylates FANCD2 and FANCI, leading to their retention on chromatin. This pathway is crucial for ICL repair and is involved in coordinating HR, NER, and TLS. The FA pathway also suppresses NHEJ to prevent spurious ligation of ICL-induced DSBs. ICL repair involves the recognition of damage by FANCM, leading to the recruitment of the FA core complex. Nucleases like FAN1, SLX4, and XPF-ERCC1 are involved in cleaving DNA adjacent to ICLs. TLS polymerases, including Pol v, REV1, and Pol ζ, are essential for bypassing ICLs. HR is critical for repairing ICLs, especially at stalled replication forks, and involves the formation of DSBs and the use of homologous sequences for repair. NHEJ is an alternative repair pathway that can lead to deletions, insertions, and translocations. However, in FA cells, the FA pathway suppresses NHEJ to prevent errors. Inhibiting NHEJ can enhance HR and reduce ICL sensitivity. Modulating ICL sensitivity through NHEJ inhibition or enhancing HR could improve cancer treatment. Understanding theDNA interstrand crosslinks (ICLs) are highly toxic DNA lesions that block DNA replication and transcription by preventing strand separation. ICL-inducing agents, such as nitrogen mustards, cisplatin, and mitomycin C, are widely used in chemotherapy. Recent research has revealed how cells repair ICLs, particularly through the Fanconi anaemia (FA) pathway, which involves nucleases, helicases, and other DNA-processing enzymes. Understanding this pathway could lead to more targeted cancer treatments and insights into drug resistance. The use of ICL-inducing agents in chemotherapy originated from the horrors of chemical warfare in WWII. The SS John Harvey, a ship carrying mustard gas, was bombed, leading to the discovery of the drug's potential in treating leukemia. Since then, ICL-inducing agents have become key in cancer treatment, though their role in causing cancer is less clear. ICLs can cause various DNA lesions, and exposure to high levels of natural ICL-inducing agents is rare. ICLs are formed by chemical reactions with bases on opposing DNA strands, leading to covalent bonds that are usually irreversible. Intrastrand crosslinks are less toxic as they can be bypassed by some DNA polymerases. The repair of ICLs involves complex coordination of DNA repair processes, including homologous recombination (HR), nucleotide excision repair (NER), and translesion synthesis (TLS). Defects in these processes can cause cancer but also sensitize cancer cells to ICL-based chemotherapy. FA is a rare genetic disorder linked to ICL sensitivity, characterized by bone marrow failure and increased cancer risk. The FA pathway involves the FA core complex, which monoubiquitylates FANCD2 and FANCI, leading to their retention on chromatin. This pathway is crucial for ICL repair and is involved in coordinating HR, NER, and TLS. The FA pathway also suppresses NHEJ to prevent spurious ligation of ICL-induced DSBs. ICL repair involves the recognition of damage by FANCM, leading to the recruitment of the FA core complex. Nucleases like FAN1, SLX4, and XPF-ERCC1 are involved in cleaving DNA adjacent to ICLs. TLS polymerases, including Pol v, REV1, and Pol ζ, are essential for bypassing ICLs. HR is critical for repairing ICLs, especially at stalled replication forks, and involves the formation of DSBs and the use of homologous sequences for repair. NHEJ is an alternative repair pathway that can lead to deletions, insertions, and translocations. However, in FA cells, the FA pathway suppresses NHEJ to prevent errors. Inhibiting NHEJ can enhance HR and reduce ICL sensitivity. Modulating ICL sensitivity through NHEJ inhibition or enhancing HR could improve cancer treatment. Understanding the