The comprehensibility of L2 texts is a major concern for English-as-a-second-language (ESL) and English-as-a-foreign-language (EFL) learners attempting to make sense of unfamiliar English texts. Conflicting research findings regarding the effectiveness of various approaches to L2 input modification can confuse educators and researchers alike. The aim of the present systematic review and network meta-analysis is to quantitatively summarize the existing research on the efficacy of simplification and elaboration input modifications for promoting L2 reading comprehension. A systematic search was performed to locate studies that examined the effect of textual simplification and elaboration input modifications using pre and post measures on L2 reading comprehension outcomes using controlled investigations from published and unpublished sources that were experimental or quasi-experimental in design. Thirty-four eligible studies were included in the final meta-analysis (n = 4742). The results of the synthesis indicate that both simplified and elaborated texts were significantly more comprehensible than authentic texts. Simplified texts were also found to be marginally more comprehensible than elaborated texts. Taking into consideration unclear risk of bias, there is sufficient evidence that input-modifications focused on text simplification and elaboration are effective for promoting L2 reading comprehension.