BACKGROUND: This study aimed to assess the conclusiveness of Cochrane Reviews (CRs) in oncology nursing. METHODS: We searched systematically for all CRs published in the Cochrane Library in the oncology nursing field between January 2014 and April 2023. We analyzed the difference between conclusive and inconclusive outcomes using the χ and Mann-Whitney -tests and identified 430 articles. However, we excluded 385 articles after reviewing their titles and abstracts. We assessed 45 full-text articles for eligibility and identified 32 articles. Of the 32 articles, we extracted 19 interventions. RESULTS: The overall outcomes were 182 cases, with 51.6% (n = 94) and 48.4% (n = 88) demonstrating conclusiveness and inconclusiveness, respectively. Regarding conclusiveness, 28.0% (n = 51) and 23.6% (n = 43) reported that the studied interventions were effective and ineffective, respectively. We found that studies on interventions related to physical activity and yoga had significantly high rates of conclusive. Compared with inconclusiveness outcomes, conclusive outcomes involved significantly more studies ( < 0.001) and patients ( < 0.001). CONCLUSIONS: Ultimately, these findings reveal that in the oncology nursing field, only 51% of the main outcomes of each nursing intervention in CRs were conclusive.