This pre-registered systematic review and meta-analysis aimed to answer if K-2 students at risk (Population) for reading impairment benefited from a response to tier 2 reading intervention (Intervention) compared to teaching as usual, (Comparator), on word decoding outcomes (Outcome), based on randomized controlled trials (Study type). Eligibility criteria were adequately sized (N > 30 per group) randomized controlled trials of tier 2 reading interventions within response to intervention targeting K-2 at risk students (percentile 40) compared with teaching as usual (TAU). Reading interventions had to be at least 20 sessions and conducted in a school setting with at least 30 students in each group and containing reading activities. Comparator could not be another intervention. Only decoding tests from Woodcock Reading Mastery Test-Revised (WRMT) and Test of Word Reading Efficiency (TOWRE) were included. Information sources: Database search was conducted 2019-05-20 in ERIC, PsycINFO, LLBA, WOS, and additionally in Google Scholar as well as a hand search in previous reviews and meta-analyses. The searches were updated on 2021-03-21. Risk of bias: Studies were assessed with Cochrane's Risk of Bias 2, R-index and funnel plots. A random-effects model was used to analyze the effect sizes (Hedges' "g"). Seven studies met the eligibility criteria but only four had sufficient data to extract for the meta-analysis. The weighted mean effect size across the four included studies was Hedges' "g" = 0.31, 95% CI [0.12, 0.50] which means that the intervention group improved their decoding ability more than students receiving TAU. A Leave-one-out analysis showed that the weighted effect did not depend on a single study. Students at risk of reading difficulties benefit from tier 2 reading intervention conducted within response to intervention regarding a small effect on the students decoding ability. Only four studies met inclusion criteria and all studies had at least some risk of bias. Tier 2 reading interventions, conducted in small groups within RtI, can to some extent support decoding development as a part of reading factors.