The problem of effective pain management in hospitals is a burning issue, but the exact mechanisms by which nursing care can lead to changes in pain outcomes in Saudi Arabia are poorly known, so a knowledge-practice gap is identified. The focus of this study was to model this effect by determining major predictors of nursing and situational moderators. The sequential explanatory mixed-methods design was taken, which included a cross-sectional survey of 295 nurses and 412 patients in three hospitals in Riyadh, and then interviews (semi-structured) with 27 people. The statistical data (quantitative data) were evaluated by descriptive statistics, correlation, and hierarchical regression, whereas qualitative data were analyzed with the help of thematic analysis. The regression equation attributed 33 percent of the variation of patient-reported pain management efficacy (F(7,404=28.94, p<0.001). The only significant positive predictors were the frequency of pain management practices ( 0.35, p<0.001) and attitudes towards pain ( 0.26, p<0.05) of nurses, but the workload was a negative predictor ( 0.12, p<0.05). Knowledge was not a specific predictor. These results were attributed to qualitative findings, which identified high workload and rigidity of protocols as systemic factors and cultural factors such as stoicism among patients to be independent of effects on pain reporting. The research concludes that actionable practice and professional attitude, rather than knowledge alone, are the mediating factors of the influence that nursing has upon the organization, and that organizational context serves as the most critical limitation to the study. These results suggested a change of direction to interventions that would mitigate the workload, reconfigure attitudes, and inculcate the culturally effective communication that would enhance pain outcomes in Saudi healthcare.