Anxiety disorders and subclinical anxiety symptoms are prevalent in childhood and adolescence, highlighting the need for prevention and early intervention efforts. While research has demonstrated positive effects for some school-based anxiety interventions, additional research is warranted to ascertain program effectiveness, composition, and delivery to best meet student needs. This multi-study dissertation project comprised of two studies. Study 1 was a systematic literature review that examined anxiety interventions for youth in school settings and updated and expanded a previous systematic review (Neil & Christenson, 2009) to more fully understand the state of the science regarding school-based anxiety programs. Randomized controlled trials (RCT) from articles published between 2008 and June 2016 were reviewed and evaluated in areas including program effectiveness, program content, intervention intensity, and participant age. Twenty-two RCTs, representing 9,693 study participants, were coded and analyzed. Results indicated that 43% of trials reported statistically significant reductions in anxiety (ES = -0.69 to -0.15) with the majority of programs based in cognitive behavioral therapy (CBT). Results from Study 1 were used to inform the development and implementation of an applied school-based anxiety intervention. In Study 2, Think Good Feel Good was implemented as a low-cost, 6-week, CBT-based modularized intervention to address student anxiety in an elementary school utilizing a multiple-baseline single case design. The main purpose was to analyze the effectiveness of the program as measured by formative and summative anxiety assessment measures following a multi-method, multi-source approach. Participants included 14 students across third, fourth, and fifth grades at a public elementary school. Results of the study indicated both responders and non-responders to the intervention. Self-report data on the Multidimensional Anxiety Scale for Children (MASC-2) pre/post assessments showed statistically significant anxiety reduction on the generalized anxiety disorder and the physical symptoms scales, whereas parent and teacher pre/post data and progress monitoring data revealed mixed findings. Social validity data from students indicated high acceptability and perceived utility. The implications of the results from this dissertation project for future research and practice are discussed.