In vivo delivery of Cas9 mRNA and sgRNAs using CRISPR‐LNPs allows for efficient gene editing, achieving up to ~70%–80% editing.Intracerebral injection of CRISPR‐LNPs targeting PLK1 (sgPLK1‐cLNPs) in aggressive orthotopic glioblastoma resulted in tumour cell apoptosis, inhibited tumour growth by 50%, and improved survival by 30%.• Selective uptake of epidermal growth factor receptor (EGFR)‐targeted sgPLK1‐cLNPs into disseminated ovarian tumours led to inhibition of tumour growth and increased survival by 80%. The gene discussed is PLK1; the disease is glioblastoma.