Purpose of this study, in which 19 trainers and 415 competitive youth field hockey and soccer players (M age=15.9, SD=1.6; 283 boys and 132 girls) selected by their age, sex, and performance status participated, was to develop a practical, reliable, and valid measure of tactical skills in sports. With trainers, 34 questions were formulated involving tactical skills. Factor analysis yielded the Tactical Skills Inventory for Sports. Scales were labeled Positioning and Deciding, Knowing about Ball Actions, Knowing about Others, and Acting in Changing Situations, covering all aspects of tactical skills regarding Declarative versus Procedural knowledge and Attack and Defense. Internal consistency and test-retest measures for reliability (except Knowing about Ball Actions) were within acceptable limits. Elite players scored better than nonelite players, supporting construct validity. The inventory is suitable for measuring tactical skills in youth field hockey and soccer players in sports practice.