Smaller formats of sided games (SSG), such as 1v1 to 4v4, are often reported to be more physically and physiologically demanding than medium-sided games (e.g., 6v6 to 8v8). However, there is a lack of experimental research examining the effects of such stimuli on physical fitness adaptations in untrained men. This study aimed to compare the effects of small-sided games (SSG) and medium-sided games (MSG) on various physical fitness parameters (e.g., outcome 1; outcome 2) in untrained men after an 8-week intervention period. A randomized controlled design was used, comparing two experimental groups with a control group that maintained a sedentary lifestyle, which was confirmed through questionnaires. Sixty men (mean age: 18.8 ± 0.74 years) volunteered for the study. The experimental groups underwent a training intervention three times per week for eight weeks. Participants in the SSG group played games ranging from 1v1 to 3v3, while those in the MSG group engaged in games from 6v6 to 8v8. Before and after the intervention, all participants completed a series of fitness assessments, including the standing long jump (SLJ), vertical jump (VJ), 10- and 30-meter sprints, change of direction (COD), and a 20-meter multi-stage fitness test (MFT). Results revealed that after eight weeks, the SSG group demonstrated significant improvements over the control group in SLJ (p < 0.01; ES = 0.642), VJ (p < 0.01; ES = 0.511), 10-meter sprint (p < 0.01; ES = 0.62), 30-meter sprint (p < 0.01; ES = 0.41), COD (p < 0.01; ES = 0.435), and 20-meter MFT (p < 0.01; ES = 0.64). Similarly, the MSG group showed significant gains compared to the control group in SLJ (p < 0.01; ES = 0.541), VJ (p < 0.01; ES = 0.439), 10-meter sprint (p < 0.01; ES = 0.451), 30-meter sprint (p < 0.01; ES = 0.25), COD (p < 0.01; ES = 0.523), and 20-meter MFT (p < 0.01; ES = 0.693). In conclusion, this study shows that both SSG and MSG are equally effective in enhancing physical fitness parameters in untrained men, despite slight variations in intensity.