How to change the Font size in UIPickerView?

You need to implement pickerView:viewForRow:forComponent:reusingView: method in picker’s delegate

- (UIView *)pickerView:(UIPickerView *)pickerView viewForRow:(NSInteger)row forComponent:(NSInteger)component reusingView:(UIView *)view{
    UILabel* tView = (UILabel*)view;
    if (!tView){
        tView = [[UILabel alloc] init];
            // Setup label properties - frame, font, colors etc
            ...
    }
    // Fill the label text here
    ...
    return tView;
}