This dataset contains the aggregated results of a meta-analysis assessing the environmental effects of marine cage aquaculture in the Western Mediterranean, based on environmental monitoring plans (EMPs) from five finfish cage farms in southeastern Spain (2017–2022). Effect sizes were calculated as logarithmic response ratios (LogRR = ln(Impact/Control)) using the escalc function from the metafor R package, and random-effects meta-analysis models were fitted using restricted maximum likelihood (REML) to compare Impact versus Control monitoring stations. The dataset reports, for each variable, the number of independent comparisons (k), the pooled effect size, its standard error, the associated p-value, and the 95% confidence interval. Two sets of variables are included: Physicochemical variables (water column and sediment): e.g. ammonium, nitrate, chlorophyll-a, dissolved oxygen, organic matter, redox potential. Biological variables (water column, sediment, and benthic habitat): e.g. macrobenthic abundance, faecal coliforms, Shannon-Wiener diversity, species richness. Raw environmental monitoring data are proprietary to the fish farming companies and were provided under confidentiality agreements; they are therefore not publicly available.