Instructions
Red/Blue/Yellow/FireRed/LeafGreen
Travel to the Safari Zone in the northern part of Fuchsia City.
Enter the Safari Zone and pay $500 to begin the catching game.
Walk around in the grass until you encounter Chansey. In "Pokemon Red," "Pokemon Blue" and "Pokemon Yellow," Chansey can be found in all areas of the Safari Zone. In "Pokemon FireRed" and "Pokemon LeafGreen," Chansey can only be found in the area 2 and the center area of the Safari Zone. Once you encounter a Chansey, you have a few options to choose from. Chansey tends to run away from battle immediately, so you may wish to throw a Safari Ball as soon as the battle starts to try to capture it. Your two other options are: throwing food at Chansey or throwing a rock at Chansey. The food will make Chansey less likely to run away, but also make it harder to catch. The rock has the opposite effect and will make Chansey even more likely to run away, but easier to catch. You may have to try several times in order to capture Chansey. Once Chansey has been captured, it will be transferred to your PC.
FireRed/LeafGreen
Travel to the Safari Zone in the western part of Cianwood City.
Pay $500 to enter the Safari Zone. When you are prompted to select the six areas you wish to visit, make sure one is the Plains area and another is the Meadows area.
Place 12 compatible objects in the Plains area.
Travel to the Meadows area and walk around until you encounter a Chansey. Throw a Safari Ball to capture it. Once you have captured Chansey, it will be transferred to your PC.