Ovarian cancer is the most lethal gynaecological malignancy, responsible for over 4,000 deaths each year in the UK. There is growing evidence that mRNA-binding proteins (RBPs) can be post-transcriptional drivers of cancer progression. Here, I investigated the expression of the RBP LARP1 in ovarian malignancies and role of the protein in ovarian cancer cell biology. LARP1 is highly expressed at both an mRNA and protein level in ovarian cancers compared with benign tumours and normal ovarian tissue. I show that higher levels of LARP1 in tumour tissue are predictive of poor patient survival. Consistent with this clinical finding, in xenograft studies knockdown of LARP1 expression causes a dramatic reduction in tumour growth. In vitro, LARP1 knockdown is associated with increased apoptosis, and is sufficient to restore platinum sensitivity in chemotherapy-resistant cell lines. Furthermore, LARP1 is required to maintain cancer stem cell marker-positive populations, and knockdown decreases tumour-initiating potential, as demonstrated by in vivo limiting dilution assays. Transcriptome deep-sequencing following LARP1 knockdown revealed altered expression of multiple genes linked to survival and evasion of apoptosis, including BCL2 and BIK. Transcripts of both genes are in complex with LARP1 protein, and LARP1 maintains the stability of BCL2 mRNA, whilst actively destabilising BIK transcripts. This effect is mediated at the level of the 3' untranslated region. I therefore conclude that by differentially regulating mRNA stability, LARP1 is a key post-transcriptional driver of tumourigenicity and cell survival in ovarian cancer.