Introduction: Anxiety is a common phenomenon that constitutes a universal cause of poor academic performance among students worldwide. It is a kind of self preoccupation which is manifested as self-minimization and results in negative cognitive evaluation, lack of concentration, unfavorable physiological reactions and academic failure. Test anxiety and its dimensions became one of the broadest research areas in recent years. Compared to other students, most of the nursing students experience high levels of test anxiety during final exam even though their marks are good throughout the semester. Objective: The aim of this study was to explore the relationship between test anxiety and academic achievement among undergraduate nursing students. Methods: A descriptive correlation, cross sectional research design was utilized to conduct the current study on a convenience sample of 277 undergraduate nursing students from all academic levels at College of Nursing, King Saud bin Abdul-Aziz University for Health Sciences--Riyadh (KSAU), who gave voluntary consent to participate in the study. Participants were asked to complete a two part questionnaire survey including participant's demographic background such as age, GPA, academic level, history of medical and mental illnesses and Test Anxiety Inventory (Spielberger, 1980) which was used to measure the primary outcome variable of the study, it is a four point Likert scale with 20 statements to find out how often participants experience the feeling described in each statement. An explanation about the purpose and the nature of the study was offered for each participant. The participants were ensured about the confidentiality and anonymity of the collected data. Data were analyzed using SPSS version 22. Results: Test anxiety score of the participants ranged between 20 and 74. Only14.4% demonstrated severe test anxiety, about 50.9% experienced moderate test anxiety and more than one quarter of the participant's experienced mild test anxiety. Analysis of data revealed statistically significant negative relationship between test anxiety scores and undergraduate nursing students' academic level (r = -0.144, p = 0.01) which explain that undergraduate nursing students in higher academic level experience less test anxiety. Pearson's R revealed a negative none statistically significant relationship (r = -0.090, p = 0.157) between test anxiety scores and undergraduate nursing students Grade Point Average. In examining the relationship between test anxiety scores and undergraduate nursing students' age, Pearson's R revealed negative none statistically significant relationship (r = -0.078, p = 0.197) which indicates that test anxiety scores decreased with participants' age. Conclusion and Recommendations: Results of this study concluded that a significant percentage of the students participated in the study experienced moderate to severe levels of test anxiety. It is fundamental to help out undergraduate nursing students to deal with stress and trim down test anxiety efficiently through group work via students, parents, faculty, academic advisors and other concerned parties. In addition undergraduate students should be taught about effective time and anxiety management strategies for better academic achievements. Considering the physiological and psychological factors leading to severe test anxiety among undergraduate nursing students is highly recommended. Counseling services should be available to nursing students when needed.