Instructions to try harder can mobilize effort and have been shown to improve performance in simple cognitive tasks (Steinborn et al., 2017), temporarily increasing the amount of cognitive resources used for the task (Kahneman, 1973). Even though such instructions are used in sports to improve athletes performance, previous research neglected to investigate their impact in more complex tasks. This study investigated whether try-harder instructions can improve performance in motor-cognitive coordination tasks of differing complexity, i.e., basketball passing movements with and without head fakes. Basketball novices and experienced players were tested to additionally investigate whether motor expertise modulates the effect of effort mobilisation. Results demonstrated that try-harder instructions improved participants performance overall, reducing response initiation and movement execution times alongside specific reduction in initiation time variability. We also found a significant interaction between the factors type of instruction (standard vs. effort) and expertise (novices vs. experienced players) [F(1,52) = 13.27, p = .038]. Post-hoc tests revealed that novices benefited more from try-harder instructions than experts, suggesting that effort mobilization yields greater improvement when motor programs are not yet fully stabilised. An analysis of the distribution of the initiation times revealed that try-harder instructions appear to enhance performance primarily by reducing attentional lapses rather than generally improving processing speed. The results of this study demonstrate that try-harder instructions to mobilise cognitive effort have the potential to improve athletes’ performance in important situations.