<![CDATA[Citizen science (CS) programs in primary education have grown substantially as an innovative approach that embeds authentic scientific inquiry into formal learning. However, systematic reviews that examine program typologies, learning outcomes, and the conditions that determine successful implementation particularly at the elementary school level are still very rare. This review classifies program typologies, maps reported learning outcomes, and identifies the key enablers and barriers to CS implementation in primary education. The study applies a systematic review methodology drawing on 18 empirical studies published between 2019 and 2025, indexed in Scopus, and focused on elementary school students aged 5 to 12, selected via the PRISMA 2020 protocol. Findings show that the contributory typology predominates (n = 8; 44%), followed by collaborative (n = 6; 33%), co-created (n = 2; 11%), and hybrid designs (n = 2; 11%). Reported learning outcomes include gains in science content knowledge, inquiry and data analysis skills, environmental awareness, and motivation. Six primary success factors were identified: iterative and structured scaffolding, trained scientist–community partnerships, digital technology integration, place-based approaches, teacher support materials, and family engagement. CS in primary education generates multidimensional learning effects, but success depends heavily on pedagogical design quality, teacher competence, and the depth of community involvement. For curriculum developers and teacher educators, the review supports prioritizing collaborative or co-created designs over purely contributory ones wherever feasible, paired with structured scaffolding; for policymakers, it identifies standardized-testing pressure as a documented barrier that protected planning time can offset; for citizen science practitioners, it points to a concrete training need, namely facilitation skills that go beyond subject-matter expertise. Future research should explore CS implementation across diverse cultural contexts, particularly in developing countries.]]>
