The focus of the research was to test the effect of Clinical Decision support on nursing evidence-based practice. The research method was quantitative with a longitudinal cluster randomized design. The study measured the effect of active clinical decision support on oncology nursing evidence-based practice in four oncology clinics associated with an academic medical center. The quasi-experimental study design contained an intervention and control group. The study intervention was active clinical decision support in the form of evidence-based drop down boxes in the nursing electronic documentation system. The total sample observations were 600, derived from a baseline sample of 200, post-education sample of 200, and a post-intervention sample of 200 observations. Electronic algorithms pulled the study sample observations randomly from the nursing documentation system database. The sample observations were nurse documented interventions for cancer-related symptoms. The interventions were scored as evidence-based or not evidence-based according to the Oncology Nursing Society (ONS) Putting Evidence Into Practice (PEP) guidelines. The study length was 11 weeks. Mixed model linear statistical analysis resulted in an F statistic for the interaction effect of study group and cycle (F(df=2,593)= 1.37, p= .255) which was not statistically significant. The average research utilization rate at baseline for both groups was 27%. After education, the average nursing evidence-based practice rate increased to 36.5% and then decreased back to 26% in the post-intervention sample. The active clinical decision support intervention did not influence an increase in nursing evidence-based practice rates.