Teaching Games for Understanding (TGfU) links tactics and skills by emphasizing the appropriate timing and application within the tactical context of the game. It has been linked to the development of enhanced tactical knowledge. The purpose of the study was to determine immediate and delayed effects of TGfU on procedural and declarative knowledge of basketball and to compare it with a technical approach. Experimental group (EG) (11 fifth graders + 18 sixth graders) was taught by TGfU and a control group (CG) (16 fifth graders + 24 sixth graders) was taught by a technical approach for 8 weeks in Physical Education (PE) classes, both. A written test was constructed to evaluate pupils’ declarative and procedural knowledge of basketball. The test was applied after the intervention to determine immediate effects and 8 months after the intervention to determine retention effects of the experimental programme. Shapiro-Wilk test, Wilcoxon T-test, Man-Whitney U-test were used for statistical analysis of obtained data. Cohen’s d was used to calculate effect size. Generally basketball knowledge was better in EG than in CG after the intervention (p<0.05) what confirms moderate effect size. When declarative and procedural knowledge were analysed separately there was no significant difference between EG and CG. Nevertheless, moderate effect sizes indicate that the data are particularly meaningful in terms of school practice. Retention effects of both approaches were similar. Total knowledge and declarative knowledge were worse after 8 months than immediately after the intervention in both groups (p<0.01). In both groups, there was no significant difference in procedural knowledge between the test written immediately after the intervention and 8 months later. Differences of changes were not significant between the groups.