At the end of levels in Kirby Tilt n' Tumble, you can hear him yell "yatta!" ("I did it!") after reaching the goal. However, I've never known him to ever say anything else other than what is seemingly gibberish (his oft-used "aaaii~" and "poyo").
Conclusion: he can speak, he just typically chooses not to. Or he only knows a single phrase.
this is racist please delete your account
Kirby sucks.
https://www.youtube.com/watch?v=t5IPpd_ZNOA
[youtube]https://www.youtube.com/watch?v=L8AoPY0tqRU[/youtube]
スカッシュ