In this study, effectiveness of 3 warm-up (WU) modes on 50m free style on child swimmers has been evaluated. In repeated-measures counterbalanced design, 10 male swimmers of a local sports club (10-12 ages) have tried out 50m freestyle after each WU on different days. Each WU took 15 minutes and the intensity of WU has been checked over by Borg's rating of perceived exertion (RPE) 15-point scale. a) no warm-up (NWU): the swimmers sat or laid down for 15 minutes, b) dryland warm-up (DWU): continuous rope-jumping at RPE 12 for 5 minutes, 2 sets 10x15s calisthenics with 15s breathing spaces and continuous rope jumping at RPE 14 for 5 minutes, c) in-water warm up (SWU): continuous freestyle swimming at RPE 12 for 5 minutes, freestyle swimming with 8x15m maximum performance with 30s breathing spaces and continuous freestyle swimming at RPE 14 for 5 minutes. RPE, stroke count and heart rate (HR) have been evaluated together with the best time in swimming performance. Compared with NWU swimming time post DWU was faster, however the fastest swimming time was achieved post SWU. After NWU swimming RPE was significantly higher. Significant difference could not be found in terms of HR and stroke count. Consequently, SWU is better for swimming performance and DWU can be used when swimming pool is not available.