Background/Context: Literacy skills are critical to understanding information presented in written or oral formats and communicating effectively with others. These skills are important to students' success in school and later in life, including improved individual health and economic outcomes, increased civic engagement, and enhanced community well-being. Therefore, identifying effective reading interventions in Spanish in the elementary grades is of great importance. Purpose/Objective/Research Question: The purpose of this review is to examine and synthetize the research evidence underlying reading interventions in Spanish across Spanish speaking countries or countries where students develop literacy in Spanish (e.g., US). Our scoping search has identified two reviews in Spanish-speaking students focusing on reading comprehension as the outcome (Balbi et al., 2018; Ripoll and Aguado, 2014). Although we will build upon those previous reviews, our review includes more stringent inclusion criteria, so that only high-quality evidence is identified and synthesized. Method: This study uses a systematic review approach (The Campbell Collaboration, 2019), which involves traditional meta-analysis techniques of systematic reviews and effect size calculations (Lipsey & Wilson, 2001). Inclusion criteria: 1. Studies must focus on Spanish as L1 and use Spanish as the language of instruction. 2. Studies must use Spanish as the target language in Spanish Speaking countries (or any other that provide equivalent conditions). 3. Studies must evaluate programs and practices implemented in pre-K-6 education. 4. Studies must compare children taught in classes using a given literacy program or practice with those in control classes using standard methods. 5. Duration of the study must be a minimum of 12 weeks or an approximately equivalent number of sessions. 6. Studies must demonstrate baseline equivalence between groups based on the analytic sample (after attrition) within +/- 0.25 SD. 7. Studies have to have at least 2 teachers/schools and 30 students in each treatment group. 8. Studies may be published without time limits. 9. No geographical restriction was included. 10. No cultural restriction was included. 11. Study reports must be available in Spanish or English. 12. No specific document type was restricted. 13. Studies must evaluate programs that could be replicated. Literature search procedure: In order to identify potential candidates for our final sample of studies meeting the inclusion criteria, two main search strategies have been conducted. A "Primary search" of databases including a wide range of electronic databases like: Web of Science (WoS), Proquest, Scopus, OvidSP, EBSCOhost, Taylor & Francis, Springer Link, Science Direct, REDINED, REDUC, ÍnDICEs-CSIC, Redalyc, Dialnet. "Complementary search" included Google Scholar, other internet engines, hand searching of relevant educational websites, literature snowballing, and contacting experts. References from previous reviews were also examined for possible inclusion as well. Various combinations of keywords, such as "reading", "Spanish", "intervention", "literacy achievement", "school", "pre-k", "K-6", "control group", "comparison group", "quasi-experiment", "randomised control design" were used to identify studies. Search results were limited to studies published until June 2020. Effect sizes: Effect sizes were calculated in terms of Hedges' g. Standardised mean difference effect sizes were calculated using procedures for Hedges' g as the difference between adjusted post-test scores for treatment and control students, divided by the pooled standard deviation of unadjusted post-test scores for treatment and control, with a correction applied for small sample sizes (Hedges, 1981). Alternative procedures were used to estimate effect sizes when unadjusted post-tests or unadjusted standard deviations were not reported, as described by Lipsey and Wilson (2001). Overall mean effect sizes were calculated across studies and programs, weighted by inverse variance, adjusted for clustering as described by Hedges (2007). We used a multivariate meta-regression model with robust variance estimation (RVE) to conduct the meta-analysis (Hedges et al., 2010). To assess the degree of heterogeneity in the effect sizes, a 95% prediction interval was calculated for each of the full meta-regressions (Borenstein et al., 2017). Findings: A total of 10 studies met the inclusion criteria for Spanish reading interventions (see Figure 1). The studies included were of high methodological quality: 9 (90%) of the studies were randomised trials and 1 (10%) was a quasi-experimental study. The full meta-regression model is shown in Table 1. For all studies, this model controlled for grade level and outcome type. There was a large, positive effect across all studies (ES = +0.33, p < 0.05).There was substantial heterogeneity across this sample, with a 95% PI of -0.16 to 0.83. Two moderators were identified and explored statistically (see Table 2). Neither grade level or outcome type were significant moderators. Conclusions: This meta-analysis provides encouraging findings, suggesting that some interventions for Spanish reading exist that can effectively help readers in K-6 education. In this vein, the present study found a large, positive effect overall, and significant impacts for the categories K-2, Reading Comprehension, and Phonological Awareness. Thus, this meta-analysis suggests that if implemented with fidelity, Spanish readers mastering core reading elements in Spanish can be improved, although the need for more rigorous interventions and evaluation research designs on reading interventions should be a national priority.