Objective. This study aims to estimate the effect size of psychological interventions for anxiety treatmentin people diagnosed with breast cancer. Method. A systematic review of online databases (Dialnet, Ebsco, Latindex, PubMed, ScienceDirect, Wiley, SAGE, Scielo, and Google Scholar) was carried out, through which experimental and quasi-experimental articles relevant to the analysis were retrieved. From the selected articles, data were extracted regarding the participants, the treatments used, and pre and post test data from the groups for analysis. Results. Seventeen articles that met the inclusion criteria were used in the analysis. The overall effect size of the interventions was determined (g = -.459). Likewise, bias and continuous moderating variables analyses were performed.Objetivo. Esta investigación busca estimar el tamaño del efecto de las intervenciones psicológicaspara el tratamiento de la ansiedad en personas con cáncer de mama. Método. Se realizó una revisión sistemática de bases de datos en línea (Dialnet, Ebsco, Latindex, PubMed, ScienceDirect, Wiley, SAGE, Scielo y Google Scholar), a través de la cual se extrajeron artículos experimentales y cuasi-experimentales relevantes para el tema de estudio. De los artículos seleccionados, se extrajeron datos de las participantes, los  tratamientos utilizados y datos pretest y postest de los grupos para el análisis. Resultados. Diecisiete artículos que cumplieron los criterios de inclusión fueron agregados en el análisis. El tamaño de efecto global de las intervenciones fue de (g = -.459). Asimismo, se realizaron análisis de sesgo y de variables continuas moderadoras.Objective. This study aims to estimate the effect size of psychological interventions for anxiety treatmentin people diagnosed with breast cancer. Method. A systematic review of online databases (Dialnet, Ebsco, Latindex, PubMed, ScienceDirect, Wiley, SAGE, Scielo, and Google Scholar) was carried out, through which experimental and quasi-experimental articles relevant to the analysis were retrieved. From the selected articles, data were extracted regarding the participants, the treatments used, and pre and post test data from the groups for analysis. Results. Seventeen articles that met the inclusion criteria were used in the analysis. The overall effect size of the interventions was determined (g = -.459). Likewise, bias and continuous moderating variables analyses were performed.Objective. This study aims to estimate the effect size of psychological interventions for anxiety treatmentin people diagnosed with breast cancer. Method. A systematic review of online databases (Dialnet, Ebsco, Latindex, PubMed, ScienceDirect, Wiley, SAGE, Scielo, and Google Scholar) was carried out, through which experimental and quasi-experimental articles relevant to the analysis were retrieved. From the selected articles, data were extracted regarding the participants, the treatments used, and pre and post test data from the groups for analysis. Results. Seventeen articles that met the inclusion criteria were used in the analysis. The overall effect size of the interventions was determined (g = -.459). Likewise, bias and continuous moderating variables analyses were performed.