Can font size of UILabel be changed with smooth animation on iPhone?

Set the font on the UILabel to be the size that you want when it is enlarged. Then scale it down. When you want the label to swell, scale it back up to it’s original size.

    messageLabel.font = [UIFont boldSystemFontOfSize:45]; 
    messageLabel.transform = CGAffineTransformScale(messageLabel.transform, 0.25, 0.25); 
    [self.view addSubview:messageLabel]; 
    [UIView animateWithDuration:1.0 animations:^{
        messageLabel.transform = CGAffineTransformScale(messageLabel.transform, 4, 4);
    }];