Small-sided games (SSGs) are widely used in soccer training to develop multiple performance domains, though interactions among design components can complicate targeting specific outcomes. This umbrella synthesis aimed to integrate findings from systematic reviews and meta-analyses to clarify how key SSG design components are associated with different training objectives and to develop an evidence-informed framework for SSG design. A synthesis of 37 systematic reviews and meta-analyses was conducted. The analysis focused on eight commonly manipulated SSG design components—Area per Player, player format, bout duration, work-to-rest ratio, rules and task constraints, touch limitation, joker usage, and directionality/goalkeeper involvement—and examined their associations with six primary performance domains: aerobic load, anaerobic/ glycolytic demands, high-speed running and sprint exposure, neuromuscular/mechanical demands, technical execution, and tactical behaviors. Consistent patterns indicate that spatial density and player format are central determinants of SSG responses. Aerobic strain is most frequently reported in formats ranging from 2 v 2 to 4 v 4, with approximately 100–150 m2 per player. In contrast, maximal sprint exposure is rarely achieved unless pitch dimensions exceed ~300–365 m2 per player, suggesting the need for complementary conditioning when maximal speed development is required. Smaller formats and restricted spaces are associated with higher acceleration–deceleration density and increased technical involvement, while rule manipulations can substantially increase internal load and game intensity. Tactical behaviors were particularly sensitive to numerical balance, directional constraints, and the use of jokers. The synthesized evidence was translated into an evidence-informed SSG design matrix that links key training components to targeted performance outcomes.