The aim of this study was to investigate the effect of pitch shape modifications on heart rate responses and time-motion characteristics in soccer players during 5-a-side small-sided games (SSGs). Players completed four different SSG dimensions: (1) short narrow pitch (SN; 40 × 25 m), (2) short wide pitch (SW; 66 × 25 m), (3) long narrow pitch (LN; 40 × 50 m), and (4) long wide pitch (LW; 66 × 50 m). Twenty amateur soccer players (age: 21 ± 5 yr; stature: 176.8 ± 1.9 cm; body mass: 72.7 ± 3.7 kg) were monitored using a heart rate monitor and a 10 Hz GPS device. Mean maximum heart rate (%HRmax), rating of perceived exertion (RPE), peak running speed, total distance covered (TD), distance covered in four speed categories, number of moderate and high accelerations (Ac), decelerations (Dc), changes of direction (COD) and player load were recorded. Increasing the pitch length had a greater effect compared to increasing the pitch width especially on RPE (3.8, 6.3, 4.9 and 6.6 AU to SN, LN, SW and LW, respectively) and time-motion characteristics such as TD (101, 127, 108 and 131 m·min-1 to SN, LN, SW and LW, respectively), peak speed (4.8, 6.1, 5.2 and 6.2 m·s-1 to SN, LN, SW and LW, respectively), and the number of accelerations, decelerations, and changes of direction. The data demonstrates that increasing the length rather than the width of 5-a-side SSG has a greater impact on players’ responses in terms of increasing workloads.