Manipulating task constraints by scaling key features like space and equipment is considered an effective method for enhancing performance development and refining movement patterns in sport. Despite this, it is currently unclear whether scaled manipulation of task constraints would impact emergent movement behaviours in young children, affording learners opportunities to develop relevant skills. Here, we sought to investigate how scaling task constraints during 8 weeks of mini tennis training shaped backhand stroke development. Two groups, control (n = 8, age = 7.2 ± 0.6 years) and experimental (n = 8, age 7.4 ± 0.4 years), underwent practice using constraints-based manipulations, with a specific field of affordances designed for backhand strokes as the experimental treatment. To evaluate intervention effects, pre- and post-test match-play characteristics (e.g. forehand and backhand percentage strokes) and measures from a tennis-specific skills test (e.g. forehand and backhand technical proficiency), were evaluated. Post intervention, the experimental group performed a greater percentage of backhand strokes out of total number of shots played (46.7 ± 3.3%). There was also a significantly greater percentage of backhand winners out of total backhand strokes observed (5.5 ± 3.0%), compared to the control group during match-play (backhands = 22.4 ± 6.5%; backhand winners = 1.0 ± 3.6%). The experimental group also demonstrated improvements in forehand and backhand technical proficiency and the ability to maintain a rally with a coach, compared to the control group. In conclusion, scaled manipulations implemented here elicited more functional performance behaviours than standard Mini Tennis Red constraints. Results suggested how human movement scientists may scale task constraint manipulations to augment young athletes' performance development.