Sister chromatid cohesion mediated by the cohesin complex is essential for chromosome segregation during cell division. Using functional genomic screening, we identify a set of 26 pre‐mRNA splicing factors that are required for sister chromatid cohesion in human cells. Loss of spliceosome subunits increases the dissociation rate of cohesin from chromatin and abrogates cohesion after DNA replication, ultimately causing mitotic catastrophe. Depletion of splicing factors causes defective processing of the pre‐mRNA encoding sororin, a factor required for the stable association of cohesin with chromatin, and an associated reduction of sororin protein level. Expression of an intronless version of sororin and depletion of the cohesin release protein WAPL suppress the cohesion defect in cells lacking splicing factors. We propose that spliceosome components contribute to sister chromatid cohesion and mitotic chromosome segregation through splicing of sororin pre‐mRNA. Our results highlight the loss of cohesion as an early cellular consequence of compromised splicing. This may have clinical implications because SF3B1, a splicing factor that we identify to be essential for cohesion, is recurrently mutated in chronic lymphocytic leukaemia. Synopsis Correct splicing of cohesin‐loading factor sororin is required for sister chromatid cohesion during interphase. Mutations in a splicing factor essential for cohesion is implicated in chronic lymphocytic leukemia. Functional genomics identifies a set of 26 spliceosome subunits that are required for sister chromatid cohesion in human cells. Loss of splicing factors increases the turnover of cohesin complexes on chromatin and abrogates sister chromatid cohesion during interphase. Compromising splicing reduces the steady‐state levels of sororin, a factor required for the stable association of cohesin with chromatin. Increasing sororin protein level or removing the cohesin release factor WAPL restores cohesion in cells lacking splicing factors. The key connections between sister chromatids in human cells are exquisitely sensitive to sororin dosage and to defects in pre‐mRNA splicing. Recurrent splicing factor mutations in hyperproliferative haematological disorders may affect cohesin turnover on chromatin. Correct splicing of cohesin‐loading factor sororin is required for sister chromatid cohesion during interphase. Mutations in a splicing factor essential for cohesion is implicated in chronic lymphocytic leukemia.