Small-sided games are used to improve tactical-technical and physical performances in team sports. This study compared the physical, physiological, and tactical-technical responses during 3 versus 3 basketball small-sided games performed in full and half-court: numerical equality (3 vs. 3), numerical superiority (4 vs. 3), and with a non-scorer floater (3 vs. 3  +  1). A total of 45 U-14 and U-15 male athletes participated in the study. They were divided into three-player teams and played one 4-minute bout of each small-sided game type. Heart rate and the time spent in four acceleration zones (0.0–0.5, 0.5–1.0, 1.0–1.5, and 1.5–2.0 g) were recorded using heart rate monitors and triaxial accelerometers. Small-sided games were filmed for the analysis of tactical-technical behavior. Results showed a higher frequency of space creation without the ball, and a mean number of passes per offense in the formats 4 versus 3 and 3 versus 3  +  1, and a lower frequency of space creation with the ball dribbled in 3 versus 3  +  1 compared with 3 versus 3. Physical and physiological responses were higher in the full-court regardless of format and in numerical equality regardless of court area; only the time spent in the highest acceleration zone was higher in half-court small-sided games. We concluded that additional players increase group tactical actions and decrease physical and physiological responses in 3 versus 3 basketball small-sided games.