Introduction Telephone crisis helplines provide around the clock support for individuals experiencing crisis situations, physical/mental illness or experiencing suicidal related behaviour. Lifeline is a telephone crisis helpline which also offers talking therapies and face-to-face counselling sessions. The objective of this study was to examine changes in ‘Clinical Outcomes in Routine Evaluation’ (CORE) scores in those who participated in talking therapy packages provided by Lifeline. CORE scores which reflect quantitative data on the individual’s psychological state (before and after completion of talking therapy) was captured using two forms of CORE measuring tools. Methods CORE assessments were carried out for 5,578 individuals before-and-after they engaged with talking therapy from Lifeline between 2013-2020. Two forms of CORE measuring tools were used (CORE-OM and CORE-10). Mean scores for each client from pre-therapy assessments were compared to mean scores from post-therapy assessments for each form of measure. Results There was a significant decrease in CORE scores (p<0.001 for CORE-OM and CORE-10) across all forms from pre-therapy to post-therapy, signifying that clients’ mental wellbeing improved as a result from talking therapies provided by Lifeline. The proportion of clients who made Reliable and Clinically Significant Improvement (RCSI), Reliable Improvement (RI) No Reliable Improvement (NRI) and Reliable Deterioration (RD) for each CORE measurement are discussed. Conclusion Results demonstrate that talking therapy packages provided by crisis helplines can be effective in reducing levels of psychological distress in those who utilise the service.